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PDO::prepare

(PHP 5 >= 5.1.0, PECL pdo >= 0.1.0)

PDO::preparePrepares a statement for execution and returns a statement object

Описание

PDOStatement PDO::prepare ( string $statement [, array $driver_options= array() ] )

Prepares an SQL statement to be executed by the PDOStatement::execute() method. The SQL statement can contain zero or more named (:name) or question mark (?) parameter markers for which real values will be substituted when the statement is executed. You cannot use both named and question mark parameter markers within the same SQL statement; pick one or the other parameter style.

You must include a unique parameter marker for each value you wish to pass in to the statement when you call PDOStatement::execute(). You cannot use a named parameter marker of the same name twice in a prepared statement. You cannot bind multiple values to a single named parameter in, for example, the IN() clause of an SQL statement.

Calling PDO::prepare() and PDOStatement::execute() for statements that will be issued multiple times with different parameter values optimizes the performance of your application by allowing the driver to negotiate client and/or server side caching of the query plan and meta information, and helps to prevent SQL injection attacks by eliminating the need to manually quote the parameters.

PDO will emulate prepared statements/bound parameters for drivers that do not natively support them, and can also rewrite named or question mark style parameter markers to something more appropriate, if the driver supports one style but not the other.

Список параметров

statement

This must be a valid SQL statement for the target database server.

driver_options

This array holds one or more key=>value pairs to set attribute values for the PDOStatement object that this method returns. You would most commonly use this to set the PDO::ATTR_CURSOR value to PDO::CURSOR_SCROLL to request a scrollable cursor. Some drivers have driver specific options that may be set at prepare-time.

Возвращаемые значения

If the database server successfully prepares the statement, PDO::prepare() returns a PDOStatement object. If the database server cannot successfully prepare the statement, PDO::prepare() emits PDOException.

Замечание: Emulated prepared statements does not communicate with the database server so PDO::prepare() does not check the statement.

Примеры

Пример #1 Prepare an SQL statement with named parameters

<?php
/* Execute a prepared statement by passing an array of values */
$sql 'SELECT name, colour, calories
    FROM fruit
    WHERE calories < :calories AND colour = :colour'
;
$sth $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY));
$sth->execute(array(':calories' => 150':colour' => 'red'));
$red $sth->fetchAll();
$sth->execute(array('calories' => 175'colour' => 'yellow'));
$yellow $sth->fetchAll();
?>

Пример #2 Prepare an SQL statement with question mark parameters

<?php
/* Execute a prepared statement by passing an array of values */
$sth $dbh->prepare('SELECT name, colour, calories
    FROM fruit
    WHERE calories < ? AND colour = ?'
);
$sth->execute(array(150'red'));
$red $sth->fetchAll();
$sth->execute(array(175'yellow'));
$yellow $sth->fetchAll();
?>

Смотрите также


User Contributed Notes
PDO::prepare
php at evan dot fribourgonline dot com
17-May-2010 05:53
Note that PDO::CURSOR_SCROLL is **not** supported or emulated by the MySQL PDO driver, nor is a warning thrown.

See: http://bugs.php.net/bug.php?id=44475
Robin
04-Mar-2010 01:01
Use prepared statements to ensure integrity of binary data during storage and retrieval. Escaping/quoting by f.e. sqlite_escape_string() or PDO::quote() is NOT suited for binary data - only for strings of text.

A simple test verifies perfect storage and retrieval with prepared statements:

<?php

$num_values
= 10000;

$db = new pdo( 'sqlite::memory:' );

$db->exec( 'CREATE TABLE data (binary BLOB(512));' );

// generate plenty of troublesome, binary data
for( $i = 0; $i < $num_values; $i++ )
{
    for(
$val = null, $c = 0; $c < 512/16; $c++ )
       
$val .= md5( mt_rand(), true );
    @
$binary[] = $val;
}

// insert each value by prepared statement
for( $i = 0; $i < $num_values; $i++ )
   
$db->prepare( 'INSERT INTO data VALUES (?);' )->execute( array($binary[$i]) );

// fetch the entire row
$data = $db->query( 'SELECT binary FROM data;' )->fetchAll( PDO::FETCH_COLUMN );

// compare with original array, noting any mismatch
for( $i = 0; $i < $num_values; $i++ )
    if(
$data[$i] != $binary[$i] ) echo "[$i] mismatch\n";

$db = null;

?>
sgirard at rossprint dot com
29-Oct-2009 11:15
Maybe everyone else already knows this but...

If you have a routine that prepares/executes many insert or update statements for a sqlite db then you may want to make use of the pdo transactions.

On some old hardware my query set went from 12 seconds to 1/3-1/2 second.

-sean
richard at codevanilla.com
11-Sep-2009 11:44
beware
PDO will emulate prepared statements/bound parameters for drivers that do not natively support them, and can also rewrite named or question mark style parameter markers to something more appropriate, if the driver supports one style but not the other.

This includes mySQL it seems so

<?php
try{
       
$sth1 = $this->db1->prepare($t1, array(PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY));
       
        }
        catch(
PDOException $e){
                return
$this->pack('dbError', $e->getMessage());
        }
?>

does not and so will not throw the exception if your SQL is wrong.

You will need to check that $sth1 is not null.
daniel dot egeberg at gmail dot com
24-May-2009 08:06
In addition to what "admin at wdfa dot co dot uk" said, you can also pass an array of values to PDOStatement::execute(). This is also secured against SQL injection. You don't necessarily have to use bindParam() or bindValue().
admin at wdfa dot co dot uk
10-Apr-2009 04:52
Note on the SQL injection properties of prepared statements.

Prepared statements only project you from SQL injection IF you use the bindParam or bindValue option.

For example if you have a table called users with two fields, username and email and someone updates their username you might run

UPDATE `users` SET `user`='$var'

where $var would be the user submitted text.

Now if you did
<?php
$a
=new PDO("mysql:host=localhost;dbname=database;","root","");
$b=$a->prepare("UPDATE `users` SET user='$var'");
$b->execute();
?>

and the user had entered  User', email='test for a test the injection would occur and the email would be updated to test as well as the user being updated to User.

Using bindParam as follows
 <?php
$var
="User', email='test";
$a=new PDO("mysql:host=localhost;dbname=database;","root","");
$b=$a->prepare("UPDATE `users` SET user=:var");
$b->bindParam(":var",$var);
$b->execute();
?>

The sql would be escaped and update the username to User', email='test'
Anonymous
26-Sep-2008 10:25
@ jacques at chester dot id dot au

If your table names are configurable (and came from a safe source, like your own config), you can easily use string concatenation to put them in a query.

If the source is unknown / unsafe, it's usually a sign of terrible design flaws. in example if you have N tables with the same set of fields, it would be much safer to make just two tables - mark (containing list of names of what "used to be" old tables) and real data (with one more column referencing key). Then, all operations on data can be performed using the db user unable to delete all your data, and (the point this all started) you know names of both tables when preparing statement, so no problem with PDO not converting/escaping it properly.

Only exception is when you're writing DB management system. Then, however, user is supported to have access to everything db user has, so SQL Injection is a cese of no gain == no problem.

As far as I understand, those were main reason nobody even thought that serious developer will need functioning table names sql injection prevention so near to db drivers.
ak_9jsz
19-May-2008 05:16
Using cursors doesn't work with SQLite 3.5.9. I get an error message when it gets to the execute() method.

Some of you might be saying "duh!" but i was surprised to see TRIGGER support in SQLite, so i had to try. :)

I wanted to use Absolute referencing on a Scrollable cursor and i only wanted one column of data. So i used this instead of a cursor.

<?php

$dbo
= new PDO('sqlite:tdb');
$sql = 'SELECT F1, F2 FROM tblA WHERE F1 <> "A";';
$res = $dbo->prepare($sql);
$res->execute();
$resColumn = $res->fetchAll(PDO::FETCH_COLUMN, 0);

for(
$r=0;$r<=3;$r++)
    echo
'Row '. $r . ' returned: ' . $resColumn[$r] . "\n";

$dbo = null;
$res = null;
?>
Stan
14-Nov-2007 03:35
Using prepared SELECT statements on a MySQL database prior to MySQL 5.1.17 can lead to SERIOUS performance degradation.

Quote from http://dev.mysql.com/doc/refman/5.1/en/query-cache.html :

>> The query cache is not used for server-side prepared statements before MySQL 5.1.17 <<

The MySQL query cache buffers complete query results and is used to satisfy repeated identical queries if the underlying tables do not change in the meantime - just what happens all the time in a typical web application. It speeds up queries by a several hundred to a several thousand percent.

Obviously, it doesn't make much sense to give up query caching for the relatively small performance benefit of prepared statements (i.e. the DBMS not having to parse and optimize the same query multiple times) - so using PDO->query() for SELECT statements is probably the better choice i you're connecting to MySQL < 5.1.17.
www.onphp5.com
07-Apr-2007 01:41
Please note that the statement regarding driver_options is misleading:

"This array holds one or more key=>value pairs to set attribute values for the PDOStatement object that this method returns. You would most commonly use this to set the PDO::ATTR_CURSOR value to PDO::CURSOR_SCROLL to request a scrollable cursor. Some drivers have driver specific options that may be set at prepare-time"

From this you might think that scrollable cursors work for all databases, but they don't! Check out this bug report:
http://bugs.php.net/bug.php?id=34625
Greg MacLellan
23-Feb-2007 06:51
A more versatile version of the below, but supporting an associative array and arbitrary number of fields:

<?php

  
public function matchCriteria($fields=null) {
      
$db=DB::conn();
      
$sql=array();
      
$paramArray=array();
       if(
is_array($fields)) {
           foreach (
$fields as $field=>$value)) {
              
$sql[] = $field.'=?';
              
$paramArray[]=$value;
           }
       }
      
$rs=$db->prepare('SELECT * FROM mytable'.(count($paramArray) ? ' WHERE '.join(' AND ',$sql) : ''));
      
$result=$rs->execute($paramArray);
       if(
$result) {
           return
$rs;
       }
       return
false;
   }

?>
johniskew
22-Feb-2007 04:03
If you need to create variable sql statements in a prepare statement...for example you may need to construct a sql query with zero, one, two, etc numbers of arguments...here is a way to do it without a lot of if/else statements needed to glue the sql together:

<?php

   
public function matchCriteria($field1=null,$field2=null,$field3=null) {
       
$db=DB::conn();
       
$sql=array();
       
$paramArray=array();
        if(!empty(
$field1)) {
           
$sql[]='field1=?';
           
$paramArray[]=$field1;
        }
        if(!empty(
$field2)) {
           
$sql[]='field2=?';
           
$paramArray[]=$field2;
        }
        if(!empty(
$field3)) {
           
$sql[]='field3=?';
           
$paramArray[]=$field3;
        }
       
$rs=$db->prepare('SELECT * FROM mytable'.(count($paramArray)>0 ? ' WHERE '.join(' AND ',$sql) : ''));
       
$result=$rs->execute($paramArray);
        if(
$result) {
            return
$rs;
        }
        return
false;
    }

?>
jacques at chester dot id dot au
13-Nov-2006 02:07
Watch out: prepared statements on MySQL barf if you try to pass in substitution tables for sql keywords, table names, view names and field names.

For example, this will not work:

$stmt = $dbh->prepare("SELECT :sqlAggregate( :fieldName) from :viewName";

You will get a MySQL error 1064 and a very unhelpful error message.

In short, you need to do string substitutions into your queries if you want configurable table names, aggregate keywords etc etc.

Which doesn't help at all in the "protection from injection attacks" thing. A very annoying discovery.
william dot clarke at gmail dot com
31-Aug-2006 10:58
Surely if you want to use prepared statements that way you should use the syntax in the second example:

eg.

instead of:
select id,name from demo_de where name LIKE :name OR name=:name

use:
select id,name from demo_de where name LIKE ? OR name=?

I believe you are supposed to either use distinct named parameters (name, name1) OR anonymous parameters (?s)
roth at egotec dot com
30-Aug-2006 08:58
Attention using MySQL and prepared statements.
Using a placeholder multiple times inside a statement doesn't work. PDO just translates the first occurance und leaves the second one as is.

select id,name from demo_de where name LIKE :name OR name=:name

You have to use

select id,name from demo_de where name LIKE :name OR name=:name2

and bind name two times. I don't know if other databases (for example Oracle or MSSQL) support multiple occurances. If that's the fact, then the PDO behaviour for MySQL should be changed.
 

 
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