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Arrays

An array in PHP is actually an ordered map. A map is a type that associates values to keys. This type is optimized for several different uses; it can be treated as an array, list (vector), hash table (an implementation of a map), dictionary, collection, stack, queue, and probably more. As array values can be other array s, trees and multidimensional array s are also possible.

Explanation of those data structures is beyond the scope of this manual, but at least one example is provided for each of them. For more information, look towards the considerable literature that exists about this broad topic.

Syntax

Specifying with array()

An array can be created by the array() language construct. It takes as parameters any number of comma-separated key => value pairs.

array(  key =>  value
     , ...
     )
// key may only be an  integer  or  string 
// value may be any value of any type
<?php
$arr 
= array("foo" => "bar"12 => true);

echo 
$arr["foo"]; // bar
echo $arr[12];    // 1
?>

A key may be either an integer or a string . If a key is the standard representation of an integer , it will be interpreted as such (i.e. "8" will be interpreted as 8, while "08" will be interpreted as "08"). Float s in key are truncated to integer . The indexed and associative array types are the same type in PHP, which can both contain integer and string indices.

A value can be any PHP type.

Note: Attempting to access an array key which has not been defined is the same as accessing any other undefined variable: an E_NOTICE-level error message will be issued, and the result will be NULL.

<?php
$arr 
= array("somearray" => array(=> 513 => 9"a" => 42));

echo 
$arr["somearray"][6];    // 5
echo $arr["somearray"][13];   // 9
echo $arr["somearray"]["a"];  // 42
?>

If a key is not specified for a value, the maximum of the integer indices is taken and the new key will be that value plus 1. If a key that already has an assigned value is specified, that value will be overwritten.

<?php
// This array is the same as ...
array(=> 433256"b" => 12);

// ...this array
array(=> 43=> 32=> 56"b" => 12);
?>
Warning

Before PHP 4.3.0, appending to an array in which the current maximum key was negative would create a new key as described above. Since PHP 4.3.0, the new key will be 0.

Using TRUE as key will evaluate to integer 1 as a key. Using FALSE as key will evaluate to integer 0 as a key. Using NULL as a key will evaluate to the empty string. Using the empty string as a key will create (or overwrite) a key with the empty string and its value; it is not the same as using empty brackets.

Array s and object s can not be used as keys. Doing so will result in a warning: Illegal offset type.

Creating/modifying with square bracket syntax

An existing array can be modified by explicitly setting values in it.

This is done by assigning values to the array , specifying the key in brackets. The key can also be omitted, resulting in an empty pair of brackets ([]).

$arr[key] = value;
$arr[] = value;
// key may be an  integer  or  string 
// value may be any value of any type

If $arr doesn't exist yet, it will be created, so this is also an alternative way to create an array . To change a certain value, assign a new value to that element using its key. To remove a key/value pair, call the unset() function on it.

<?php
$arr 
= array(=> 112 => 2);

$arr[] = 56;    // This is the same as $arr[13] = 56;
                // at this point of the script

$arr["x"] = 42// This adds a new element to
                // the array with key "x"
                
unset($arr[5]); // This removes the element from the array

unset($arr);    // This deletes the whole array
?>

Note: As mentioned above, if no key is specified, the maximum of the existing integer indices is taken, and the new key will be that maximum value plus 1. If no integer indices exist yet, the key will be 0 (zero).
Note that the maximum integer key used for this need not currently exist in the array . It need only have existed in the array at some time since the last time the array was re-indexed. The following example illustrates:

<?php
// Create a simple array.
$array = array(12345);
print_r($array);

// Now delete every item, but leave the array itself intact:
foreach ($array as $i => $value) {
    unset(
$array[$i]);
}
print_r($array);

// Append an item (note that the new key is 5, instead of 0).
$array[] = 6;
print_r($array);

// Re-index:
$array array_values($array);
$array[] = 7;
print_r($array);
?>

The above example will output:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)
Array
(
)
Array
(
    [5] => 6
)
Array
(
    [0] => 6
    [1] => 7
)

Useful functions

There are quite a few useful functions for working with arrays. See the array functions section.

Note: The unset() function allows removing keys from an array . Be aware that the array will not be reindexed. If a true "remove and shift" behavior is desired, the array can be reindexed using the array_values() function.

<?php
$a 
= array(=> 'one'=> 'two'=> 'three');
unset(
$a[2]);
/* will produce an array that would have been defined as
   $a = array(1 => 'one', 3 => 'three');
   and NOT
   $a = array(1 => 'one', 2 =>'three');
*/

$b array_values($a);
// Now $b is array(0 => 'one', 1 =>'three')
?>

The foreach control structure exists specifically for array s. It provides an easy way to traverse an array .

Array do's and don'ts

Why is $foo[bar] wrong?

Always use quotes around a string literal array index. For example, $foo['bar'] is correct, while $foo[bar] is not. But why? It is common to encounter this kind of syntax in old scripts:

<?php
$foo
[bar] = 'enemy';
echo 
$foo[bar];
// etc
?>

This is wrong, but it works. The reason is that this code has an undefined constant (bar) rather than a string ('bar' - notice the quotes). PHP may in future define constants which, unfortunately for such code, have the same name. It works because PHP automatically converts a bare string (an unquoted string which does not correspond to any known symbol) into a string which contains the bare string . For instance, if there is no defined constant named bar, then PHP will substitute in the string 'bar' and use that.

Note: This does not mean to always quote the key. Do not quote keys which are constants or variables, as this will prevent PHP from interpreting them.

<?php
error_reporting
(E_ALL);
ini_set('display_errors'true);
ini_set('html_errors'false);
// Simple array:
$array = array(12);
$count count($array);
for (
$i 0$i $count$i++) {
    echo 
"\nChecking $i: \n";
    echo 
"Bad: " $array['$i'] . "\n";
    echo 
"Good: " $array[$i] . "\n";
    echo 
"Bad: {$array['$i']}\n";
    echo 
"Good: {$array[$i]}\n";
}
?>
The above example will output:
Checking 0: 
Notice: Undefined index:  $i in /path/to/script.php on line 9
Bad: 
Good: 1
Notice: Undefined index:  $i in /path/to/script.php on line 11
Bad: 
Good: 1

Checking 1: 
Notice: Undefined index:  $i in /path/to/script.php on line 9
Bad: 
Good: 2
Notice: Undefined index:  $i in /path/to/script.php on line 11
Bad: 
Good: 2

More examples to demonstrate this behaviour:

<?php
// Show all errors
error_reporting(E_ALL);

$arr = array('fruit' => 'apple''veggie' => 'carrot');

// Correct
print $arr['fruit'];  // apple
print $arr['veggie']; // carrot

// Incorrect.  This works but also throws a PHP error of level E_NOTICE because
// of an undefined constant named fruit
// 
// Notice: Use of undefined constant fruit - assumed 'fruit' in...
print $arr[fruit];    // apple

// This defines a constant to demonstrate what's going on.  The value 'veggie'
// is assigned to a constant named fruit.
define('fruit''veggie');

// Notice the difference now
print $arr['fruit'];  // apple
print $arr[fruit];    // carrot

// The following is okay, as it's inside a string. Constants are not looked for
// within strings, so no E_NOTICE occurs here
print "Hello $arr[fruit]";      // Hello apple

// With one exception: braces surrounding arrays within strings allows constants
// to be interpreted
print "Hello {$arr[fruit]}";    // Hello carrot
print "Hello {$arr['fruit']}";  // Hello apple

// This will not work, and will result in a parse error, such as:
// Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'
// This of course applies to using superglobals in strings as well
print "Hello $arr['fruit']";
print 
"Hello $_GET['foo']";

// Concatenation is another option
print "Hello " $arr['fruit']; // Hello apple
?>

When error_reporting is set to show E_NOTICE level errors (by setting it to E_ALL, for example), such uses will become immediately visible. By default, error_reporting is set not to show notices.

As stated in the syntax section, what's inside the square brackets ('[' and ']') must be an expression. This means that code like this works:

<?php
echo $arr[somefunc($bar)];
?>

This is an example of using a function return value as the array index. PHP also knows about constants:

<?php
$error_descriptions
[E_ERROR]   = "A fatal error has occured";
$error_descriptions[E_WARNING] = "PHP issued a warning";
$error_descriptions[E_NOTICE]  = "This is just an informal notice";
?>

Note that E_ERROR is also a valid identifier, just like bar in the first example. But the last example is in fact the same as writing:

<?php
$error_descriptions
[1] = "A fatal error has occured";
$error_descriptions[2] = "PHP issued a warning";
$error_descriptions[8] = "This is just an informal notice";
?>

because E_ERROR equals 1, etc.

So why is it bad then?

At some point in the future, the PHP team might want to add another constant or keyword, or a constant in other code may interfere. For example, it is already wrong to use the words empty and default this way, since they are reserved keywords.

Note: To reiterate, inside a double-quoted string , it's valid to not surround array indexes with quotes so "$foo[bar]" is valid. See the above examples for details on why as well as the section on variable parsing in strings.

Converting to array

For any of the types: integer , float , string , boolean and resource , converting a value to an array results in an array with a single element with index zero and the value of the scalar which was converted. In other words, (array)$scalarValue is exactly the same as array($scalarValue).

If an object is converted to an array , the result is an array whose elements are the object 's properties. The keys are the member variable names, with a few notable exceptions: integer properties are unaccessible; private variables have the class name prepended to the variable name; protected variables have a '*' prepended to the variable name. These prepended values have null bytes on either side. This can result in some unexpected behaviour:

<?php

class {
    private 
$A// This will become '\0A\0A'
}

class 
extends {
    private 
$A// This will become '\0B\0A'
    
public $AA// This will become 'AA'
}

var_dump((array) new B());
?>

The above will appear to have two keys named 'AA', although one of them is actually named '\0A\0A'.

Converting NULL to an array results in an empty array .

Comparing

It is possible to compare arrays with the array_diff() function and with array operators.

Examples

The array type in PHP is very versatile. Here are some examples:

<?php
// This:
$a = array( 'color' => 'red',
            
'taste' => 'sweet',
            
'shape' => 'round',
            
'name'  => 'apple',
            
4        // key will be 0
          
);

$b = array('a''b''c');

// . . .is completely equivalent with this:
$a = array();
$a['color'] = 'red';
$a['taste'] = 'sweet';
$a['shape'] = 'round';
$a['name']  = 'apple';
$a[]        = 4;        // key will be 0

$b = array();
$b[] = 'a';
$b[] = 'b';
$b[] = 'c';

// After the above code is executed, $a will be the array
// array('color' => 'red', 'taste' => 'sweet', 'shape' => 'round', 
// 'name' => 'apple', 0 => 4), and $b will be the array 
// array(0 => 'a', 1 => 'b', 2 => 'c'), or simply array('a', 'b', 'c').
?>

Example #1 Using array()

<?php
// Array as (property-)map
$map = array( 'version'    => 4,
              
'OS'         => 'Linux',
              
'lang'       => 'english',
              
'short_tags' => true
            
);
            
// strictly numerical keys
$array = array( 7,
                
8,
                
0,
                
156,
                -
10
              
);
// this is the same as array(0 => 7, 1 => 8, ...)

$switching = array(         10// key = 0
                    
5    =>  6,
                    
3    =>  7
                    
'a'  =>  4,
                            
11// key = 6 (maximum of integer-indices was 5)
                    
'8'  =>  2// key = 8 (integer!)
                    
'02' => 77// key = '02'
                    
0    => 12  // the value 10 will be overwritten by 12
                  
);
                  
// empty array
$empty = array();         
?>

Example #2 Collection

<?php
$colors 
= array('red''blue''green''yellow');

foreach (
$colors as $color) {
    echo 
"Do you like $color?\n";
}

?>

The above example will output:

Do you like red?
Do you like blue?
Do you like green?
Do you like yellow?

Changing the values of the array directly is possible since PHP 5 by passing them by reference. Before that, a workaround is necessary:

Example #3 Collection

<?php
// PHP 5
foreach ($colors as &$color) {
    
$color strtoupper($color);
}
unset(
$color); /* ensure that following writes to
$color will not modify the last array element */

// Workaround for older versions
foreach ($colors as $key => $color) {
    
$colors[$key] = strtoupper($color);
}

print_r($colors);
?>

The above example will output:

Array
(
    [0] => RED
    [1] => BLUE
    [2] => GREEN
    [3] => YELLOW
)

This example creates a one-based array.

Example #4 One-based index

<?php
$firstquarter  
= array(=> 'January''February''March');
print_r($firstquarter);
?>

The above example will output:

Array 
(
    [1] => 'January'
    [2] => 'February'
    [3] => 'March'
)

Example #5 Filling an array

<?php
// fill an array with all items from a directory
$handle opendir('.');
while (
false !== ($file readdir($handle))) {
    
$files[] = $file;
}
closedir($handle); 
?>

Array s are ordered. The order can be changed using various sorting functions. See the array functions section for more information. The count() function can be used to count the number of items in an array .

Example #6 Sorting an array

<?php
sort
($files);
print_r($files);
?>

Because the value of an array can be anything, it can also be another array . This enables the creation of recursive and multi-dimensional array s.

Example #7 Recursive and multi-dimensional arrays

<?php
$fruits 
= array ( "fruits"  => array ( "a" => "orange",
                                       
"b" => "banana",
                                       
"c" => "apple"
                                     
),
                  
"numbers" => array ( 1,
                                       
2,
                                       
3,
                                       
4,
                                       
5,
                                       
6
                                     
),
                  
"holes"   => array (      "first",
                                       
=> "second",
                                            
"third"
                                     
)
                );

// Some examples to address values in the array above 
echo $fruits["holes"][5];    // prints "second"
echo $fruits["fruits"]["a"]; // prints "orange"
unset($fruits["holes"][0]);  // remove "first"

// Create a new multi-dimensional array
$juices["apple"]["green"] = "good"
?>

Array assignment always involves value copying. Use the reference operator to copy an array by reference.

<?php
$arr1 
= array(23);
$arr2 $arr1;
$arr2[] = 4// $arr2 is changed,
             // $arr1 is still array(2, 3)
             
$arr3 = &$arr1;
$arr3[] = 4// now $arr1 and $arr3 are the same
?>

User Contributed Notes
Arrays
william at cycronsystems dot com
09-Jun-2010 11:28
I couldn't find a way to Trim an array in PHP so i wrote this little function that seemed to do the trick. It will trim the array down to a specified size

<?php

       
//Utility Function to Trim Array
       
function trim_array(array $array,$int){
           
$newArray = array();
            for(
$i=0; $i<$int; $i++){
               
array_push($newArray,$array[$i]);
            }
            return (array)
$newArray;
        }

?>

Example:
var_dump($treatList);
 array(3) {
    ["id"]=>
    string(3) "476"
    ["categoryID"]=>
    string(2) "49"
    ["title"]=>
    string(55) "80% off Sidewalk Crawling Classes from Urban Adventures"

$treatList = trim_array($listist,2);
Will result in:
var_dump($treatList);
 array(2) {
    ["id"]=>
    string(3) "476"
    ["categoryID"]=>
    string(2) "49"
zachera
03-Jun-2010 07:39
function array_closest_key($needle,$haystack){
    foreach($haystack as $key => $value){
        if($needle <= $value){
            return $key;
        }
    }
}

Get the closest key to the specified $needle out of $haystack.
dtomasiewicz at gmail dot com
12-May-2010 05:42
<?php
   
/**
     * Functions for examining and manipulating matrices (n-dimensional arrays) of data
     * with string dot-separated paths. For example, you might do this with multidimensional
     * array:
     *   $var = $array['someKey']['cats']['dogs']['potato'];
     *
     * Accomplishing this can be a nightmare if you don't know the depth of the path or the array
     * is of a variable dimension.
     *
     * You can accomplish the same by using $array as a Matrix:
     *   $array = new Matrix($array);
     *   $var = $array->get('someKey.cats.dogs.potato);
     *  
     * @author Daniel Tomasiewicz <www.fourstaples.com>
     */
   
class Matrix {
        private
$data;
       
        public function
__construct(array $data = array()) {
           
$this->data = $data;
        }
       
       
/**
         * Gets the value at the specified path.
         */
       
public function get($path = null) {
            if(
$path === null) {
                return
$this->data;
            }
           
           
$segs = explode('.', $path);
           
           
$target =& $this->data;
            for(
$i = 0; $i < count($segs)-1; $i++) {
                if(isset(
$target[$segs[$i]]) && is_array($target[$segs[$i]])) {
                   
$target =& $target[$segs[$i]];
                } else {
                    return
null;
                }
            }
           
            if(isset(
$target[$segs[count($segs)-1]])) {
                return
$target[$segs[count($segs)-1]];
            } else {
                return
null;
            }
        }
       
       
/**
         * Sets a value to a specified path. If the provided value is
         * null, the existing value at the path will be unset.
         */
       
public function set($path, $value = null) {
            if(
is_array($path)) {
                foreach(
$path as $p => $v) {
                   
$this->set($p, $v);
                }
            } else {
               
$segs = explode('.', $path);
           
               
$target =& $this->data;
                for(
$i = 0; $i < count($segs)-1; $i++) {
                    if(!isset(
$target[$segs[$i]])) {
                       
$target[$segs[$i]] = array();
                    }
                   
                   
$target =& $target[$segs[$i]];
                }
           
                if(
$segs[count($segs)-1] == '*') {
                    foreach(
$target as $key => $value) {
                       
$target[$key];
                    }
                } elseif(
$value === null && isset($target[$segs[count($segs)-1]])) {
                    unset(
$target[$segs[count($segs)-1]]);
                } else {
                   
$target[$segs[count($segs)-1]] = $value;
                }
            }
        }
       
       
/**
         * Returns a flattened version of the data (one-dimensional array
         * with dot-separated paths as its keys).
         */
       
public function flatten($path = null) {
           
$data = $this->get($path);
           
            if(
$path === null) {
               
$path = '';
            } else {
               
$path .= '.';
            }
           
           
$flat = array();
                       
            foreach(
$data as $key => $value) {
                if(
is_array($value)) {
                   
$flat += $this->flatten($path.$key);
                } else {
                   
$flat[$path.$key] = $value;
                }
            }
           
            return
$flat;
        }
       
       
/**
         * Expands a flattened array to an n-dimensional matrix.
         */
       
public static function expand($flat) {
           
$matrix = new Matrix();
           
            foreach(
$flat as $key => $value) {
               
$matrix->set($key, $value);
            }
           
            return
$matrix;
        }
    }
?>
john at nowhere dot com
18-Dec-2009 05:33
If you ever wondered if you can do something like:

<?php
$a
= function_that_returns_an_array()['some_index']['some_other_index'] ;
?>

The answer is no, you can't. But you can use the following function. I named it i() because it's a short name and stands for "to index".

<?php

/**
 * Usage: i( $array, $index [, $index2, $index3 ...] )
 *
 * This is functionally equivalent to $array[$index1][$index2][$index3]...
 * 
 * It can replace the more prolix
 *
 *   $tmp = some_function_that_returns_an_array() ;
 *   $value = $tmp['some_index']['some_other_index'] ;
 *
 * by doing the job with a single line of code as in
 *
 *   $value = i( some_function_that_returns_an_array(), 'some_index', 'some_other_index' ) ;
 *
 * Note that since this function is slower than direct indexing, it should only be used in cases like the one
 * described above, for improving legibility.
 *
 * @param $array
 * @param $index
 * @param [optional] $index2, index3, ...
 * @throws Exception when the indexes do not exist
 */
function i(){
   
$args = func_get_args();
   
$array = $args[0];//gets the fist parameter, $array
   
$indexes = $args;
    unset(
$indexes[0]);//because indexes[0] is actually not an index, but the first parameter, $array
   
foreach( $indexes as $index ){
        if( (!
is_array($array)) || (! array_key_exists( $index, $array )) ){
            throw new
Exception("Array index out of bounds. Parameters:".print_r($args,true));           
        }
       
$array = $array[$index];
    }
    return
$array;       
}

?>
aaron at tekserve dot com
25-Oct-2009 01:16
Here's a function to recursively convert objects to arrays and remove the special characters from private and protected variables. I use it with XML_Serializer to convert objects to XML.

<?php
function object_to_array($mixed) {
    if(
is_object($mixed)) $mixed = (array) $mixed;
    if(
is_array($mixed)) {
       
$new = array();
        foreach(
$mixed as $key => $val) {
           
$key = preg_replace("/^\\0(.*)\\0/","",$key);
           
$new[$key] = object_to_array($val);
        }
    }
    else
$new = $mixed;
    return
$new;       
}
?>
unix at bujanoci dot net
20-Oct-2009 05:55
Just in case someone finds it usefull.
If you want to capitalize the first letter of each word in the array you could:
<?php
$myarray
= array("one","two","three","four","etc..");

$map = array_map('ucfirst', $myarray);

$j = join(' , ', $map);
echo
$j;
?>

This will return:  One , Two , Three , Four , Etc..
Probably it's not worth of posting it, but just thought beginners might find it usefull.
Anonymous
02-Oct-2009 11:33
This is a modification of a function like this which works with two dimensional arrays. Pass a 2d array to this function and my function will return an array of the arrays with the specified key-value pair (specified by $key and $value).

<?php
function seekKey($array, $key, $value)
{
   
$ret = array();
    for (
$i=0;$i<count($array);$i++)
    {
        if (
$array[$i][$key]==$value)
           
$ret[] = $array[$i];
    }
    return
$ret;
}
?>
Martin
28-Sep-2009 06:04
You can actually create arrays in arrays; just consider the following code:

<?php
function LoadData($file)
    {
   
$lines = file($file) or die('Could not open file');
foreach(
$lines as $line)
        {
       
$i[] = array($line);
print_r($i[1])
}
LoadData('file.csv');

?>

A (.csv-)file is loaded into the function LoadData and stored in the array $lines. Then foreach puts the values from the $lines-array into $line and $i is defined as an array of the array $line. Please note that this type of code could take up much of CPU-usage; it generates a multi-dimensional array.

When $i is printed (in the example, value 1 of the array) it would display:

Array ( [0] => Array (
[0] => 7;75;X;0;0;1;0;3;Gr;Br;Do;0;0;0;0;0;0;0;0;
[1] => ;200;K;0;0;0;0;0;Gr;0;0;0;0;ZL;0;0;0;0;0;
[2] => ;260;Z;;;;;;Gr;;;;;VL;;;;;;
[3] => ;270;K;;;;1;;Gr;Br;Li;;;;;;;;;
[4] => ;500;V;;;;;;Br;;;;;;;;;;;
[5] => 6;60;X;;;;;;;;;;;;;;;;;
[6] => ;80;K;;;;;;Gr;;;;;ZL;;;;;;
[7] => ;210;Z;;;;;;Gr;;;;;;;;;;;
)
Ant-1
13-Jul-2009 04:12
Note for PHP 5.3 changed behavior in 'erroneous' array creation:

Prior to PHP 5.3, this array definition (note the duplicate key):
<?php $a = array ('foo' => 1, 'bar' => 2, 'foo' => 3); ?>

Would create the following array:
array(
    'foo' => 3,
    'bar' => 2
)
So the /second/ key in the duplicate would override the first declaration.

Now with PHP 5.3, the following array will be created:
array(
    'foo' => 1,
    'bar' => 2
)

So the second duplicate key would be ignored.

Note that the array declaration indeed contains an error, but if your legacy code contains such array declaration, you will be hurt because of the changed behavior.
webmaster at oehoeboeroe dot nl
05-May-2009 02:47
A simple function to check if you can use your variable as an array offset validly and without getting it typecasted.

<?php
function is_safe_offset($offset) {
    return
array_pop(@array_flip(array($offset => 0))) === $offset;
}

$a = 8;
var_dump(is_safe_offset($a));  // true

$b = '8';
var_dump(is_safe_offset($b));  // false

$c = '08';
var_dump(is_safe_offset($c));  // true

$d = 'foo';
var_dump(is_safe_offset($d));  // true

$e = 3.8;
var_dump(is_safe_offset($e));  // false

$f = false;
var_dump(is_safe_offset($f));  // false

$g = null;
var_dump(is_safe_offset($g));  // false

$h = array();
var_dump(is_safe_offset($h));  // false

$i = new StdClass;
var_dump(is_safe_offset($i));  // false
?>
genix at arctoz dot de
07-Mar-2009 12:41
Hello,

to check if an element was set is actually pretty simple:

<?php

$array
= ('first' => 1,
         
'sec' => 2
        
);

$out = (isset($array['third'])) ? $array['third'] : 'third not set...';

echo
$out;
?>

greets,
genix
Dawid Krysiak
17-Dec-2008 11:09
Trying to get array element that was not set, throws ERROR_NOTICE and returns NULL. Example:
<?php /* php v.4.4.7 */
$array = array(
   
'apple' => 'green',
   
'orange' => 'orange',
);
$pear_color = $array['pear'];    // Notice: Undefined index: pear in /path/to/file.php on line 123
var_dump($pear_color);        // NULL
?>
Haven't found that mentioned on this page.
hek at theeks dot net
24-Oct-2008 03:58
Note that NULL is not exactly a scalar value, so the following two lines of code do NOT produce identical arrays.

<?php
$x
= (array) null; // $x ends up an empty array (zero elements)
$y = array(null); // $y ends up an array containing one element (a null)
?>
pinkgothic at gmail dot com
13-Sep-2008 03:49
Re: fmouse,

the phenomenom you're describing pertains to superglobals, not arrays, and it only applies in a very specific scope. Check out http://de.php.net/manual/en/language.variables.variable.php :

"Please note that variable variables cannot be used with PHP's Superglobal arrays within functions or class methods. The variable $this is also a special variable that cannot be referenced dynamically."
frywater
04-Jun-2008 11:43
>fmouse

Variable variables can be used with arrays as discussed in the variable variable section.
Also, from your code, $somevar can be an array and still work fine.

$fum = "somevar";
$$fum = array(); // $somevar is now an array
$foo = $$fum;
print_r( $foo); // we get an empty array printed

print_r() doesn't just print arrays, it prints any variable type.
If you pass it a variable, that hasn't been defined yet, it won't know how to print it.

You would get this same results by passing any undefined variable such as:
print_r( $bar );  // PHP Notice: undefined variable ...$bar
fmouse at fmp dot com
29-Apr-2008 08:14
Using variables as array names no longer works in PHP5.

$fum = "somevar";
$foo = $$fum;

# Still works if $somevar isn't an array.  $foo contains the value of $somevar

but ....

$fum = "_POST";
print_r($$fum);
print_r(${$fum});

Neither form of indirection works in this context.  $$fum comes back empty.

If you have PHP4 code that used this kind of indirection you can work around the change in PHP5 using an eval().

$fum = "_POST";
$foo = eval("return $$fum;");
print_r($foo);

This works!
rama dot devi at gmail dot com
18-Mar-2008 09:52
Sorting double dimensional arrays by a specified key bothe for Strings and for integers:
Ex:
 
 $personDetails =  array( array("firstName" => "Nancy", "lastName" => "Grace", "age" => 22), array("firstName" => "Andy",  "lastName" => "Peter", "age" => 28),                           array("firstName" => "Jim",   "lastName" => "Gary",  "age" => 25), array("firstName" => "Lary",  "lastName" => "James", "age" => 28),  array("firstName" => "Peter", "lastName" => "David", "age" => 17), array("firstName" => "Raj",   "lastName" => "King",  "age" => 9),                           array("firstName" => "John",  "lastName" => "Baxter","age" => 35) );
//To sort the array by firstName:-
     function sortFirstName($p1, $p2) {
          return strnatcmp($p1['firstName'], $p2['firstName']);
      }
      usort($personDetails, 'sortFirstName');

//To sort by an integer Field

   function sortByInteger(&$personDetails, $field) {
      $sort = "return strnatcmp(\$p1['$field'], \$p2['$field']);";
       usort($personDetails, create_function('$p1,$p2', $sort));
        return $personDetails;
    }

    $personDetails = sortByInteger($personDetails, 'age');
//To sort the array in Descending order by a key, It can be done by adding "-" sign before strnatcmp() function.

I hope this helps
ken underscore yap atsign email dot com
09-Jan-2008 04:00
"If you convert a NULL value to an array, you get an empty array."

This turns out to be a useful property. Say you have a search function that returns an array of values on success or NULL if nothing found.

$values = search(...);

Now you want to merge the array with another array. What do we do if $values is NULL? No problem:

$combined = array_merge((array)$values, $other);

Voila.
pepesantillan at gmail dot com
19-Dec-2007 12:25
z on 22-Apr-2005 12:10 wrote:
-----------------------------------------------
Here's a simple function to insert a value into some position in an array

<?php
function array_insert($array,$pos,$val)
{
   
$array2 = array_splice($array,$pos);
   
$array[] = $val;
   
$array = array_merge($array,$array2);
  
    return
$array;
}
?>

and now for example...
<?php
$a
= array("John","Paul","Peter");
$a = array_insert($a,1,"Mike");
?>

Now $a will be "John","Mike","Paul","Peter"
-----------------------------------------------

Im learning to use PHP and reading about array_splice found that

<?php
function array_insert($array,$pos,$val)
{
   
$array2 = array_splice($array,$pos);
   
$array[] = $val;
   
$array = array_merge($array,$array2);

    return
$array;
}

$a = array("John","Paul","Peter");
$a = array_insert($a,1,"Mike");
print_r($a);
?>

would output the same as

<?php
$b
= array("John","Paul","Peter");
array_splice($b,1,0,array("Mike"));
print_r($b);
?>
SID TRIVEDI
10-Oct-2007 09:14
<?php

//Simple Login Script using associative array.

//You may modify the codes and use $_POST['FORM_FIELD_DATA'] for your web-page.
//You may spice-up the codes with more form field validation & security features.

//$user_name=$_POST['user_name'];
//$password=$_POST['password'];

$test_user_name = 'michelle_smith'; //for testing purpose only
$test_password = 'msmith321';        //for testing purpose only
$user_name = $test_user_name;
$password = $test_password;

// here user_name is key and password is the value of an array..
// website owner has to add new user/site member manually in $login_array

$login_array = array(
               
'user_name' => 'password',
               
'alex_duff' => 'alx321',
                   
'xena78' => 'xena321',
               
'dela_pena' => 'delp321',
               
'shawn_1981' => 'shw81',
               
'michelle_smith' => 'msmith321');

ksort ($login_array);
reset($login_array);
if (isset(
$login_array[$user_name]))
{
$pass_check = $login_array[$user_name];
if (
$password === $pass_check)
{
echo 
"Welcome, $user_name!\n<br>"; //may redirect to specific webpage.
}
else
{
echo
"Please try again!"; //may redirect to Error page.
}
}
else
{
    echo
"Please register with us. Thanks!"; //may redirect to registration page.
   
exit();
   
}
echo(
"\n<br>");
echo
'Thanks to Thies C. Arntzen, Stig Bakken, Shane Caraveo, Andi Gutmans, Rasmus Lerdorf, Sam Ruby, Sascha Schumann, Zeev Suraski, Jim Winstead, Andrei Zmievski for wonderful PHP!';

?>
carl at linkleaf dot com
06-Sep-2007 06:36
Its worth noting that there does not appear to be any functional limitations on the length or content of string indexes. The string indexes for your arrays can contain any characters, including new line characters, and can be of any length:

<?php

$key
= "XXXXX";
$test = array($key => "test5");

for (
$x = 0; $x < 500; $x++) {
 
$key .= "X";
 
$value = "test" . strlen($key);
 
$test[$key] = $value;
}

echo
"<pre>";
print_r($test);
echo
"</pre>";

?>

Keep in mind that using extremely long array indexes is not a good practice and could cost you lots of extra CPU time. However, if you have to use a long string as an array index you won't have to worry about the length or content.
Gautam
30-Aug-2007 08:56
<?php
//EXAMPLE  of Multi-Dimentional Array where as an array's keys are an array itself.
//It's so easy to create one like this.

$movie_to_watch = array ('Action'=>
          array(
'Kanu Reeves' => 'Matrix Reloaded',
                     
'Pearce Brosnan' => 'Die Another Day',
                     
'Tom Cruz' => 'Mission Impossible',
                     
'Jason Statham' => 'Crank',
                     
'Danzel Washington' => 'Man on Fire'),
               
'Comedy' =>
                array (
'Charlie Chaplin' => 'City Lights',
                      
'Jim Carrey'    => 'Cable Guy',
                      
'Rowan Atkinson' => 'The Ultimate Disaster'));
$type_wanted = 'Action'; //You may switch type from Action to Comedy.
$hero_wanted = 'Pearce Brosnan'; // You may switch hero from Pearce Brosnan to Jim Carrey.

print ("$hero_wanted 's  $type_wanted movie is " . $movie_to_watch[$type_wanted][$hero_wanted].".");
// produces browser output as under:
// Pearce Brosnan 's Action movie is Die Another Day.
?>
Olegk, getmequick[at]gmail[dot]com
21-Aug-2007 09:59
Hey..

here is a function which helps to avoid using empty/isset
checkings for arrays.

(it's acts simillar to 'default' modifier in Smarty)

Using this function you will avoid 'Undefined index' or
'Undefined offset' error.

<?php

$_POST
['id']['other'] = 'val1';

/*
key exist (same as $_POST['id'][other])
*/
echo getRequestParam('id[other]', 'default value');

/*
key doesn't exist, we get default value (same as $_POST['var'])
*/

echo getRequestParam('var', 'default value');

function
getRequestParam( $var, $default = '', $method = 'post' )
{
   
preg_match_all('!(\w+)!i',$var, $match );
   
array_shift($match);
   
$_vars = $match[0];
   
$ret = null;   
   
    if(    
strtoupper($method)   ==  'POST' ) {
       
$ret = _findRequestParam($_vars, $_POST);
    }
    elseif(
strtoupper($method) == 'GET' ) {
       
$ret = _findRequestParam($_vars, $_GET);
    }
    elseif(
strtoupper($method) == 'COOKIE' ) {
       
$ret = _findRequestParam($_vars, $_COOKIE);
   
    }
    elseif(
strtoupper($method) == 'SESSION' ) {
       
$ret = _findRequestParam($_vars, $_SESSION);
    }   
   
    if (!
$ret )
          return
$default;
    else
        return
$ret;       
   
}

/**
@access private
*/

function _findRequestParam($vars, $find_in , $curr_key = 0)
{
    static
$ret;
   
    if(
array_key_exists($vars[$curr_key], $find_in) ) {
        if(
count( $vars)-1 == $curr_key ) {
           
$ret $find_in[$vars[$curr_key]];
        }
        elseif(
$curr_key < count( $vars)-1 ) {
           
_findRequestParam( $vars, $find_in[$vars[$curr_key]], $curr_key+ );       
        }   
    }

    return
$ret;

}

?>

Hope this will help someone!
conorj
14-Jul-2007 03:34
Another note on unquoted array indices. Because it is first interpreted as a constant, it must obey the naming convention of constants. i.e. a letter or underscore followed by optional letter, digit and/or underscore characters.

Therefore while the following array declaration is legal:
$a = array('1st'=>'First','2nd'=>'Second');

Trying to access either array item as follows causes an error:

$first = "$a[1st]";
$second = "$a[2nd]";
moehbass at gmail dot com
11-Jul-2007 12:41
<b>Mark Gukov</b> wrote below:

Regarding the fact that there's no need to quote arrays keys when enclosed in double quotes: it only applies to single dimensional arrays.

The following works fine:

<?php
$r
['a'] = 'apple';
echo
"$r[a] is tasty.";
?>

...but in the case of multi-dimensional arrays:

<?php
$r
['a']['b'] = 'banana';
echo
"$r[a][b] is tasty.";
?>

would result in "Array[c] is tasty."
-----------------------------------------------------------------

However, the following runs fine;
$r['a']['b'] = 'banana';
echo "{$r[a][b]} is tasty.";

Just box it!
don dot hosek at gmail dot com
24-May-2007 12:37
It's slightly faster to use array_splice to remove an element of an array:
array_splice($array, $index, 1)
than to do it using the suggested method of unset and reindex:
unset($array[$index]);
$array = array_values($array);

The difference, however, is very small. With 950 iterations I had times of
unset and reindex: 0.22837495803833
splice: 0.22392416000366
lesantoso at yahoo dot com
20-Mar-2007 10:14
This Indonesian number speller function is twice
faster(*) than the one provided in class Terbilang by
anghuda(at)gmail(dot)com (25-May-2006 08:52):

http://www.lesantoso.com/terbilang.html

(*) 2.1 vs. 4.2 seconds in processing 10000 random numbers
Spudley
16-Mar-2007 09:44
On array recursion...

Given the following code:

<?
$myarray
= array('test',123);
$myarray[] = &$myarray;
print_r($myarray);
?>

The print_r() will display *RECURSION* when it gets to the third element of the array.

There doesn't appear to be any other way to scan an array for recursive references, so if you need to check for them, you'll have to use print_r() with its second parameter to capture the output and look for the word *RECURSION*.

It's not an elegant solution, but it's the only one I've found, so I hope it helps someone.
kal at kalunite dot com i mean dot net
17-Jan-2007 01:55
About the automatic conversion of bare strings...
My opinion is that it never should have been implemented. Isn't it easier to NOT implement this "handy" feature in the first place? It is such a convenient way for "smart" programmers to write unsafe, not-futureproof code. Please remove this feature from future versions of PHP, please. (Hey, if you could change the OOP mechanisms between PHP 4 and PHP 5, why can't you make this change, right?)
25-Oct-2006 04:18
This page should include details about how associative arrays are implemened inside PHP; e.g. using hash-maps or b-trees.

This has important implictions on the permance characteristics of associative arrays and how they should be used; e.g. b-tree are slow to insert but handle collisions better than hashmaps.  Hashmaps are faster if there are no collisions, but are slower to retrieve when there are collisions.  These factors have implictions on how associative arrays should be used.
Mark Gukov
27-Sep-2006 09:18
Regarding the fact that there's no need to quote arrays keys when enclosed in double quotes: it only applies to single dimensional arrays.

The following works fine:

<?php
$r
['a'] = 'apple';
echo
"$r[a] is tasty.";
?>

...but in the case of multi-dimensional arrays:

<?php
$r
['a']['b'] = 'banana';
echo
"$r[a][b] is tasty.";
?>

would result in "Array[c] is tasty."
petruzanautico at yahoo dot com dot ar
21-Sep-2006 03:30
Regarding the message of phoenixbytes:

The line foreach($bad as $baddies); will just yield in $baddies the last value of the array $bad.
I think that wasn't your intention, in that case there are faster and better ways than foreach.

I think what you wanted to do is:
<?php
foreach($bad as $baddies) // make a collection
{
    if (
preg_match("/$baddies/i", $mailto)) // find a match
   
{
   
$addrmail = "false";
    }
    else
    {
   
$addrmail = "true";
    }
}
// foreach end
?>
php dot net at todandlorna dot com
25-Jul-2006 11:28
in response to ch dot martin at gmail dot com

If you are using the following code:

<?php
$r
= array('05' => "abc", '35' => "def");
foreach (
$r as $key=>$value)
  
var_dump($key);
?>

and you need the array key '35' to be a string (for looping maybe), you can make sure the key is a string by appending a 0 on the front.

'035' instead of '35'
ch dot martin at gmail dot com
09-Jun-2006 06:40
Extremely irritating quirk regarding the variable types of array keys:

<?php
$r
= array('05' => "abc", '35' => "def");
foreach (
$r as $key=>$value)
   
var_dump($key);
?>

The first var_dump for '05' is:
    string(2) "05"
as expected.  But the second, '35', turns out as:
    int(35)

Php apparently decided to make the 35 became an int, but not the 05 (presumably because it leads with a zero).  As far as I can see, there is absolutely no way of making string(2) "35" an array key.
anghuda(at)gmail(dot)com
25-May-2006 01:52
this is simpler tha function display_angka_bilangan by ktaufik(at)gmail(dot)com (16-Feb-2005 12:40)

<?

/*
*
* Class : Terbilang
* Spell quantity numbers in Indonesian or Malay Language
*
*
* author: huda m elmatsani
* 21 September 2004
* freeware
*
* example:
* $bilangan = new Terbilang;
* echo $bilangan -> eja(137);
* result: seratus tiga puluh tujuh
*
*
*/

Class Terbilang {

    function
terbilang() {
       
$this->dasar = array(1=>'satu','dua','tiga','empat','lima','enam',
       
'tujuh','delapan','sembilan');

       
$this->angka = array(1000000000,1000000,1000,100,10,1);
       
$this->satuan = array('milyar','juta','ribu','ratus','puluh','');
    }

    function
eja($n) {

   
$i=0;
    while(
$n!=0){

       
$count = (int)($n/$this->angka[$i]);

        if(
$count>=10) $str .= $this->eja($count). " ".$this->satuan[$i]." ";
        else if(
$count > 0 && $count < 10)
           
$str .= $this->dasar[$count] . " ".$this->satuan[$i]." ";

           
$n -= $this->angka[$i] * $count;
           
$i++;
        }
       
$str = preg_replace("/satu puluh (\w+)/i","\\1 belas",$str);
       
$str = preg_replace("/satu (ribu|ratus|puluh|belas)/i","se\\1",$str);

        return
$str;
    }
}

?>
benjcarson at digitaljunkies dot ca
09-May-2006 08:46
phoenixbytes: The regex you have posted for matching email addresses is incorrect.  Among other things, it does not allow '+' before the '@' (which is perfectly valid and can be quite useful to separate extensions of a single address).  RFC 822 [1] defines the grammar for valid email addresses, and (the extemely long) regex implementing can be found at [2].  Even the "Add Note" page here at php.net says:

[quote]
And if you're posting an example of validating email addresses, please don't bother. Your example is almost certainly wrong for some small subset of cases. See this information from O'Reilly Mastering Regular Expressions book for the gory details.
[/quote]

A note to others: please do your homework before writing another email-matching regex.

[1] http://www.ietf.org/rfc/rfc0822.txt?number=822
[2] http://www.ex-parrot.com/~pdw/Mail-RFC822-Address.html.
phoenixbytes at o2 dot co dot uk
17-Apr-2006 12:10
i use the array() function for deciding upon an email address's validity, i have a 'wap stalker' of my site that loves to exploit every hole i leave, so i used the following script to avoid being email bombed with my own file sender script, the array() is used to filter out undesirable email providers and, of course, any and all of my own addresses. before all that i used a REGEX to make sure it's an actual email address before going any further.

$mailto = "mail.domain.org"; // the input to be tested

if (preg_match("/^[A-Z0-9._%-]+@[A-Z0-9._%-]+\.[A-Z]{2,6}$/i", $mailto)) // see if it's really an email address
{
    $bad = array('mytrashmail.com', 'mymail.ro', 'acasa.ro', 'gala.net', 'phoenixbytes'); // pick out the victims
    foreach($bad as $baddies); // make a collection

    if (preg_match("/$baddies/i", $mailto)) // find a match
    {
    $addrmail = "false";
    }
    else
    {
    $addrmail = "true";
    }

}
else
{
$addrmail = "false";
}

$addrmail can then be used in an argument.
$baddies can be used to give a list, if necessary.

i hope this helps someone.
crozzer
01-Apr-2006 08:54
Passing variables into the array constructor:
Just a NOOB pointer, I couldn't find other examples for this.  If you want to pass the value of an existing variable into the array() constructor, you can quote it or not, both methods are valid.

<?
$foo_value
= 'foo string';
$bar_value = 'bar string';

$myArray = array(
   
'foo_key' => $foo_value,     // not quoted
   
'bar_key' => "$bar_value");   // quoted

foreach ($myArray as $k => $v) {
   echo
"\$myArray[$k] => $v.<br />\n";
}
?>

Both of these will work as expected, but the unqoted $foo_value method above is marginally faster because adding quotes adds an additional string de-reference.
sales at maboom dot ch
13-Dec-2005 05:41
if you need to check a multidimensonal array for values it's handy to store it like

$ar['key1'][0]
$ar['key2'][0]
$ar['key3'][0]

$ar['key1'][1]
$ar['key2'][1]
$ar['key3'][1]

and to loop the keys.

Fill the array (from a database-request):

while($rf=mysql_fetch_row($rs))

{
    $nr=$rf[0];
    $channel['nr'][$nr]=$rf[1];
    $channel['chatter'][$nr]=$rf[2];
}

Call the values:

foreach(array_keys($channel['nr']) as $test)
{
print ' nr:'.$test.'<br>';
print 'value nr: '.$channel['nr'][$test].'<br>';
print ' chatter: '.$channel['chatter'][$test].'<br>';
}

This is useful, if you have to look later for an element
inside the array:

if(in_array($new_value,$channel['nr'])) print 'do something.';

Hope this helps someone.
ia [AT] zoznam [DOT] sk
30-Sep-2005 09:55
Regarding the previous comment, beware of the fact that reference to the last value of the array remains stored in $value after the foreach:

<?php
foreach ( $arr as $key => &$value )
{
   
$value = 1;
}

// without next line you can get bad results...
//unset( $value );

$value = 159;
?>

Now the last element of $arr has the value of '159'. If we remove the comment in the unset() line, everything works as expected ($arr has all values of '1').

Bad results can also appear in nested foreach loops (the same reason as above).

So either unset $value after each foreach or better use the longer form:

<?php
foreach ( $arr as $key => $value )
{
   
$arr[ $key ] = 1;
}
?>
stochnagara at hotmail dot com
27-Sep-2005 08:53
Regarding the previous comment, thw following code does the job:

<?php
foreach($arr as $key => &$value) {
  
$value = 1;
}
?>
jazepstein OverAt GeeMail dot com
19-Sep-2005 01:14
Regarding the previous comment, the fact that this code has no effect is perfectly expected:

<?php
foreach($arr as $value) {
  
$value = 1;
}
?>

The reason that this doesn't work, is because each time that PHP goes through the loop, it _copies_ the value of the array element into $value. So if you assign a new value to the data in $value, it has no effect on the actual array, because you only changed the value of the copy that was put in $value.

As was discovered in the previous post, the only way to get around this problem is to change the value in the original array. Hence, a typical foreach should instead look like this:

<?php
foreach($arr as $key => $value) {
  
$arr[$key] = 1;
}
?>
caifara aaaat im dooaat be
28-Aug-2005 09:28
[Editor's note: You can achieve what you're looking for by referencing $single, rather than copying it by value in your foreach statement. See http://php.net/foreach for more details.]

Don't know if this is known or not, but it did eat some of my time and maybe it won't eat your time now...

I tried to add something to a multidimensional array, but that didn't work at first, look at the code below to see what I mean:

<?php

$a1
= array( "a" => 0, "b" => 1 );
$a2 = array( "aa" => 00, "bb" => 11 );

$together = array( $a1, $a2 );

foreach(
$together as $single ) {
   
$single[ "c" ] = 3 ;
}

print_r( $together );
/* nothing changed result is:
Array
(
    [0] => Array
        (
            [a] => 0
            [b] => 1
        )
    [1] => Array
        (
            [aa] => 0
            [bb] => 11
        )
) */

foreach( $together as $key => $value ) {
   
$together[$key]["c"] = 3 ;
}

print_r( $together );

/* now it works, this prints
Array
(
    [0] => Array
        (
            [a] => 0
            [b] => 1
            [c] => 3
        )
    [1] => Array
        (
            [aa] => 0
            [bb] => 11
            [c] => 3
        )
)
*/

?>
uzakufuklar at hotmail dot com
04-Aug-2005 06:24
It is a kind of simple muti-dimensional array list.
 I have made it just to give a simple idea.
<?php
echo "Here we'll see how to create a multi-dimensional array.\n";
$a=array('fruits'=>array('a'=>'orange',
                     
'b'=>'grape',c=>'apple'),
           
'numbers'=>array(1,2,3,4,5,6),
           
'holes'=>array('first',5=>'second',
                                                         
'third')
            );
foreach(
$a as $list=>$things){
    foreach(
$things as $newlist=>$counter){
    echo
$counter;
    }
}
?>
z
22-Apr-2005 07:10
Here's a simple function to insert a value into some position in an array

<?php
function array_insert($array,$pos,$val)
{
   
$array2 = array_splice($array,$pos);
   
$array[] = $val;
   
$array = array_merge($array,$array2);
   
    return
$array;
}
?>

and now for example...
<?php
$a
= array("John","Paul","Peter");
$a = array_insert($a,1,"Mike");
?>

Now $a will be "John","Mike","Paul","Peter"
jeff splat codedread splot com
21-Apr-2005 04:16
Beware that if you're using strings as indices in the $_POST array, that periods are transformed into underscores:

<html>
<body>
<?php
    printf
("POST: "); print_r($_POST); printf("<br/>");
?>
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
    <input type="hidden" name="Windows3.1" value="Sux">
    <input type="submit" value="Click" />
</form>
</body>
</html>

Once you click on the button, the page displays the following:

POST: Array ( [Windows3_1] => Sux )
roland dot swingler at transversal dot com
05-Apr-2005 03:24
Something that tripped me up:

If you mix string and integer keys, be careful if you are doing a comparison on the to find if a string key exists.

For example, this will not do what you expect it to do:

<?php
$exampleArray
= array();
$exampleArray['foo'] = 'bar';
$exampleArray[] = 'Will create 0 index';

$keyWeAreLookingFor = "correctKey";

foreach (
$exampleArray as $key => $value){
  if (
$key == $keyWeAreLookingFor){
    print
"Found Key";
  }
}
?>

It will print "Found Key", because (I presume) when PHP makes the comparison between the string "correctKey" and the index 0, it casts the string to an integer, rather than casting 0 to the string "0" and then doing the comparison.

Using === fixes the problem:

<?php
foreach ($exampleArray as $key => $value){
  if (
$key === $keyWeAreLookingFor){
    print
"Found Key";
  }
}
?>
lars-phpcomments at ukmix dot net
28-Mar-2005 04:40
Used to creating arrays like this in Perl?

@array = ("All", "A".."Z");

Looks like we need the range() function in PHP:

<?php
$array
= array_merge(array('All'), range('A', 'Z'));
?>

You don't need to array_merge if it's just one range:

<?php
$array
= range('A', 'Z');
?>
mortoray at ecircle-ag dot com
16-Feb-2005 08:59
On array copying a deep copy is done of elements except those elements which are references, in which case the reference is maintained.  This is a very important thing to understand if you intend on mixing references and recursive arrays.

By Example:
    $a = array( 1 );
    $aref_a = array( &$a );
    $copy_aref_a = $aref_a;
    $acopy_a = array( $a );
    $copy_acopy_a = $acopy_a;

    $a[] = 5;
    $acopy_a[0][] = 6;

    print_r( $aref_a ); //Shows: ( (1,5) )
    print_r( $copy_aref_a ); //Shows: ( (1,5) )
    print_r( $acopy_a ); //Shows: ( (1, 6) )
    print_r( $copy_acopy_a ); //Shows: ( (1) )
ktaufik(at)gmail(dot)com
16-Feb-2005 08:40
For you who works for localized "say" number to letter ( ex , 7=> seven, 8=>eight) for Bahasa Indonesia.

Indonesia "say" or "Terbilang" is based on 3 digit number.
thousands, millions and trillions .... will be based on the 3 digit number.

In Indonesia you say 137 as "Seratus Tiga Puluh Tujuh"

<?php
//build random 3 digit number to be "said" in Bahasa Indonesia
$x=rand(0,9);
$y=rand(0,9);
$z=rand(0,9);

function
display_angka_bilangan($n) {
  
$angka = array(
    
1 => 'satu',
    
2 => 'dua',
    
3 => 'tiga',
    
4 => 'empat',
    
5 => "lima",
    
6 => 'enam',
    
7 => 'tujuh',
    
8 => 'delapan',
    
9 => 'sembilan'
  
);
   return
$angka[$n];
}
// Terbilang X-------Say X
if ($x==1){$terbilangx="seratus ";}
elseif (
$x==0){$terbilangx='';}
else {
$terbilangx=''.display_angka_bilangan($x).' '.'ratus ';}
// Terbilang Y ------Say Y
if ($y==0){$terbilangy='';}
elseif (
$y==1 && $z==1){$terbilangy="sebelas";$terbilangz='';}
elseif (
$y==1 && $z==0){$terbilangy="sepuluh ";$terbilangz='';}
elseif (
$y==1 && $z!==1 &&  $z!==0){$terbilangy=''.display_angka_bilangan($z).' belas ';}
else {
$terbilangy=''.display_angka_bilangan($y).' '.'puluh ';}
// Terbilang z ------Say z
if ($z==0){$terbilangz="";}
elseif (
$z==0 && $y==1){$terbilangz="";}
elseif (
$z==1 && $y==1){$terbilangz="";}
elseif(
$y==0) {$terbilangz="".display_angka_bilangan($z);}
elseif (
$y==1 && $z!==1 &&  $z!==0) {$terbilangz="";}
else {
$terbilangz="".display_angka_bilangan($z);};

$terbilang=$terbilangx.$terbilangy.$terbilangz;
echo
$x.$y.$z." ";
echo
$terbilang;
?>

Hope it is useful
ktaufik(at)gmail(dot)com
db
05-Jan-2005 03:06
[Editor's Note: (Second example.) These are not "arrays in arrays". These are single-dimensional arrays containing stdClass objects; all objects are referenced by default in PHP5. You can see in the var_dump output that they point to the same object.]

Attention with Arrays in Arrays!

If you copy (=) an array which contains arrays it will be REFERENCED not COPIED.

Example:

<?php
/* GOOD ONE */
echo "<b>Here copy (=) works correct:</b><br>";
/* Initialise Array 1 */
$x1 = array(array(10,20),array(30,40));
/* COPY Array */
$x2 = $x1;
/* Change some values in Array 2 */
$x2[0][0]=77;
$x2[1][1]=99;
echo
"<b>Original:</b><pre>";
var_dump($x1);
echo
"</pre><b>Changed Copy:</b><pre>";
var_dump($x2);

/* BAAAAAAAD ONE */
echo "</pre><hr><b>Here copy (=) FAILS:</b><br>";
/* Initialise Array 1 */
$a1[0]->bla[0]->id=10;
$a1[0]->bla[1]->id=20;
$a1[1]->bla[0]->id=30;
$a1[1]->bla[1]->id=40;
/* COPY Array */
$a2 = $a1;
/* Change some values in Array 2 (!) */
$a2[0]->bla[0]->id=77;
$a2[1]->bla[1]->id=99;
echo
"<b>Original:</b><pre>";
var_dump($a1);
echo
"</pre><b>Changed Copy:</b><pre>";
var_dump($a2);
echo
"</pre>";

php?>

The output of $a1 and $a2 will be the same..
Joe Morrison <jdm at powerframe dot com>
08-Nov-2004 09:26
Programmers new to PHP may find the following surprising:

<?php

$x
[1] = 'foo';
$x[0] = 'bar';
echo
"Original array:\n";
var_dump($x);

array_pop($x);
echo
"Array after popping last element:\n";
var_dump($x);

?>

The surprise is that element 0 is deleted, not element 1. Apparently the notion of "last element" has more to do with how the array is stored internally than with which element has the highest numeric index. I recently translated a Perl program to PHP and was bitten by this one.

My solution was to identify all the places in my code where I could prove that the array elements were assigned sequentially. In those cases it is safe to use array_pop, array_splice, etc. since the array indices correspond with the array layout. For the other cases, my solution was to write replacements for the built-in array functions such as this one:

<?php

function safe_pop(&$a)
{
  if (!isset(
$a))
    return;

  if (!
is_array($a))
    return;

  if (
count($a) == 0)
    return;

  unset(
$a[max(array_keys($a))]);
}

?>
Cameron Brown
19-Nov-2003 04:51
Negative and positive array indices have different behavior when it comes to string<->int conversion.  1 and "1" are treated as identical indices, -1 and "-1" are not.  So:

$arr["1"] and $arr[1] refer to the same element.
$arr["-1"] and $arr[-1] refer to different elements.

The following code:

<?
  $arr
[1]    = "blue";
 
$arr["1"]  = "red";
 
$arr[-1]   = "blue";
 
$arr["-1"] = "red";

 
var_dump($arr);
?>

produces the output:

array(3) {
  [1]=>
  string(3) "red"
  [-1]=>
  string(4) "blue"
  ["-1"]=>
  string(3) "red"
}

This code should create an array with either two or four elements.  Which one should be the "correct" behavior is an exercise left to the reader....
akamai at veloxmail dot com dot br
16-Jul-2003 11:22
It is quite simple, but don't forget when you'll using foreach with forms arrays.

If your field name is:
<input type="checkbox" name="foo['bar'][]" ...
It doesn't work.

This should work:
<input type="checkbox" name="foo[bar][]" ...
agape_logos at shaw dot ca
11-Jul-2003 11:59
I was having trouble getting javascript arrays and php arrays to work together with a Check All checkboxe.  Here is a simple solution.  Clicking the 'Check All' checkbox will check all checkboxes on the form.

<script language="JavaScript">
function chkAll(frm, arr, mark) {
  for (i = 0; i <= frm.elements.length; i++) {
    try{
      if(frm.elements[i].name == arr) {
        frm.elements[i].checked = mark;
      }
    } catch(er) {}
  }
}
</script>

<form name='foo'>
<input type="checkbox" name="ca" value="1" onClick="chkAll(this.form, 'formVar[chkValue][]', this.checked)">
<?php
for($i = 0; $i < 5; $i++){
echo(
"<input type='checkbox' name='formVar[chkValue][]' value='$i'>");
}
?>
</form>

Dean M.
chroniton .at. gmx .dot. li
26-Mar-2003 06:13
I didn't find this anywhere in the docs and i think it is worth a mention:

$a[] = &$a;
print_r($a);

// will output:

/*
Array
(
    [0] => Array
 *RECURSION*
)

*/

// this means that $a[0] is a reference to $a ( that is detected by print_r() ). I guess this is what the manual calls 'recursive arrays'.
07-Mar-2003 11:28
"Using NULL as a key will evaluate to an empty string. Using an emptry string as key will create (or overwrite) a key with an empty string and its value, it is not the same as using empty brackets."

If you create an array like this:
$foo = array(null => 'bar');
And then want to access 'bar', you must use this syntax:
echo $foo['']; // notice the two single quotes

This will of course cause a fatal error:
echo $foo[];
wmoranATpotentialtechDOTcom
29-Nov-2002 11:10
Dereferencing arrays takes some time, but is not terribly expensive.
I wrote two dummy loops to test performance:
for ($i =0; $i < count($a); $i++) {
 $x = $a[$b[$i]];
 $y = $a[$b[$i]];
 $z = $a[$b[$i]];
}
for ($i =0; $i < count($a); $i++) {
 $q = $b[$i];
 $x = $a[$q];
 $y = $a[$q];
 $z = $a[$q];
}

The first loop is 6.5% slower than the second.  Meaning that dereferencing arrays is not terribly expensive, unless you do it a whole lot. I would expect that each extra reference costs about 3% in speed. The lesson is that if you're going to be using a specific value in an array for a number of operations, you can gain a little speed by assigning it to a temp variable (or creating a reference with $q = &$b[$i]) but it's not worth getting crazy over.
I tested this with iterations of 10,000 and 100,000 on php 4.2 and the results were consistent.
mu at despammed dot com
15-Oct-2002 06:50
Recursive arrays and multi-dimensional arrays are the same thing and completely identical.

The following confirms this:

$fruits1["european"]["green"] = "Apple";
$fruits2 = array ( "european"  => array ( "green" => "Apple"));
print ($fruits1 === $fruits2);

Result: 1 (= true)
hramrach_L at centrum. cz ;-)
11-Jun-2002 12:40
Arrays can be merged using + as discussed in the notes for array_merge.
 https://doc0.ru/phpe/function.array-merge.php
philip at boone dot at
25-May-2002 01:06
For all of you having problems when using php arrays in an HTML form input field name, and wanting to validate the form using javascript for example, it is much easier to specify an id for the field as well, and use this id for validation.

Example:

<input type="text" id="lastname" name="fields[lastname]">

then in the javascript check:

if(formname.lastname.value == "") {
     alert("please enter a lastname!");
}

This works very well. If you have any problems with it, let me know.
 

 
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