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hexdec

(PHP 4, PHP 5)

hexdecHexadecimal to decimal

Description

number hexdec ( string $hex_string )

Returns the decimal equivalent of the hexadecimal number represented by the hex_string argument. hexdec() converts a hexadecimal string to a decimal number.

hexdec() will ignore any non-hexadecimal characters it encounters.

Parameters

hex_string

The hexadecimal string to convert

Return Values

The decimal representation of hex_string

Changelog

Version Description
Since 4.1.0 The function can now convert values that are too big for the platforms integer type, it will return the value as float instead in that case.

Examples

Example #1 hexdec() example

<?php
var_dump
(hexdec("See"));
var_dump(hexdec("ee"));
// both print "int(238)"

var_dump(hexdec("that")); // print "int(10)"
var_dump(hexdec("a0")); // print "int(160)"
?>

See Also


User Contributed Notes
hexdec
Rosberg - rosberglinhares at gmail dot com
06-May-2010 03:45
The correct version is:

function bchexdec($hex) {
    static $hexdec = array(
        "0" => 0,
        "1" => 1,
        "2" => 2,
        "3" => 3,
        "4" => 4,
        "5" => 5,
        "6" => 6,
        "7" => 7,
        "8" => 8,
        "9" => 9,
        "A" => 10,
        "B" => 11,
        "C" => 12,
        "D" => 13,
        "E" => 14,
        "F" => 15
    );

    $dec = 0;

    for ($i = strlen($hex) - 1, $e = 1; $i >= 0; $i--, $e = bcmul($e, 16)) {
        $factor = $hexdec[$hex[$i]];
        $dec = bcadd($dec, bcmul($factor, $e));
    }

    return $dec;
}
flurinj at gmx dot net
06-Apr-2010 02:13
Here My version of converting a hex string to a signed decimal value:

<?php

function hexdecs($hex)
{
   
// ignore non hex characters
   
$hex = preg_replace('/[^0-9A-Fa-f]/', '', $hex);
   
   
// converted decimal value:
   
$dec = hexdec($hex);
   
   
// maximum decimal value based on length of hex + 1:
    //   number of bits in hex number is 8 bits for each 2 hex -> max = 2^n
    //   use 'pow(2,n)' since '1 << n' is only for integers and therefore limited to integer size.
   
$max = pow(2, 4 * (strlen($hex) + (strlen($hex) % 2)));
   
   
// complement = maximum - converted hex:
   
$_dec = $max - $dec;
   
   
// if dec value is larger than its complement we have a negative value (first bit is set)
   
return $dec > $_dec ? -$_dec : $dec;
}

?>
Halit YEL - halityesil at globya dot net
02-Oct-2009 08:30
RGB to Hex
Hex to RGB
Function

<?PHP

function rgb2hex2rgb($c){
   if(!
$c) return false;
  
$c = trim($c);
  
$out = false;
  if(
preg_match("/^[0-9ABCDEFabcdef\#]+$/i", $c)){
     
$c = str_replace('#','', $c);
     
$l = strlen($c) == 3 ? 1 : (strlen($c) == 6 ? 2 : false);

      if(
$l){
         unset(
$out);
        
$out[0] = $out['r'] = $out['red'] = hexdec(substr($c, 0,1*$l));
        
$out[1] = $out['g'] = $out['green'] = hexdec(substr($c, 1*$l,1*$l));
        
$out[2] = $out['b'] = $out['blue'] = hexdec(substr($c, 2*$l,1*$l));
      }else
$out = false;
             
   }elseif (
preg_match("/^[0-9]+(,| |.)+[0-9]+(,| |.)+[0-9]+$/i", $c)){
     
$spr = str_replace(array(',',' ','.'), ':', $c);
     
$e = explode(":", $spr);
      if(
count($e) != 3) return false;
        
$out = '#';
         for(
$i = 0; $i<3; $i++)
           
$e[$i] = dechex(($e[$i] <= 0)?0:(($e[$i] >= 255)?255:$e[$i]));
             
         for(
$i = 0; $i<3; $i++)
           
$out .= ((strlen($e[$i]) < 2)?'0':'').$e[$i];
                 
        
$out = strtoupper($out);
   }else
$out = false;
         
   return
$out;
}

?>

Output

#FFFFFF =>
 Array{
   red=>255,
   green=>255,
   blue=>255,
   r=>255,
   g=>255,
   b=>255,
   0=>255,
   1=>255,
   2=>255
 }
 

#FFCCEE =>
 Array{
   red=>255,
   green=>204,
   blue=>238,
   r=>255,
   g=>204,
   b=>238,
   0=>255,
   1=>204,
   2=>238
 }
CC22FF =>
 Array{
   red=>204,
   green=>34,
   blue=>255,
   r=>204,
   g=>34,
   b=>255,
   0=>204,
   1=>34,
   2=>255
 }

0 65 255 => #0041FF
255.150.3 => #FF9603
100,100,250 => #6464FA


[EDIT BY danbrown AT php DOT net - Contains multiple bugfixes by (ajim1417 AT gmail DOT com) on 27-JAN-2010: Replaces typo in explode() and updates eregi() calls to preg_match().]
jose dot rob dot jr at gmail dot com
16-Aug-2009 03:13
I made these functions to pack up to 64 ID's into a mysql unsigned bigint.

ID's cannot repeat, must be <= bit's limit and > 0.

The functions uses php 32 bit's int as unsigned because we don't actually read the number, just the bits. Then 0xFFFFFFFF display -1 but the bit's are there (tested with linux 2.6 i686 and x86_64)

---

This is an other way to make hex to bin conversions:

<?php
function hexbin($hex, $padding = false)
{
   
// Validation
   
$hex = preg_replace('/^(0x|X)?/i', '', $hex);
   
$hex = preg_replace('/[[:blank:]]/', '', $hex);
    if(empty(
$hex))
    {
       
$hex = '0';
    }
    if(!
preg_match('/^[0-9A-F]*$/i', $hex))
    {
       
trigger_error('Argument is not a hex', E_USER_WARNING);
        return
false;
    }
   
   
// Conversion
   
$bin = '';
   
$hex = array_reverse(str_split($hex));
    foreach(
$hex as $n)
    {
       
$n = hexdec($n);
        for(
$i = 1; $i <= 8; $i <<= 1)
        {
           
$bin .= ($i & $n)? '1' : '0';
        }
        if(
$padding)
        {
           
$bin .= ' ';
        }
    }
    return
ltrim(strrev($bin));
}

// Tests
echo "<b>Debug:</b> <pre>";

// Randomly choosed padded number
var_dump(hexbin('00FF FF8F 7F3F FF1F', true));
// string(79) "0000 0000 1111 1111 1111 1111 1000 1111 0111 1111 0011 1111 1111 1111 0001 1111"

// Yellow RGB
var_dump(hexbin('0xF8F800'));
// string(24) "111110001111100000000000"

// Green RGB (padded)
var_dump(hexbin('0x008800', true));
//string(29) "0000 0000 1000 1000 0000 0000"

die("\n<br>debug");

?>

Have fun ;D
Ultimater at gmail dot com
19-Apr-2009 08:54
hexdec doesn't accept numbers following the period.
What if you have a number like c20.db18?
<?php
function floatinghexdec($str)
{
    list(
$intgr,$hex)=explode('.',$str,2);
   
$intgr=ereg_replace("[^A-Fa-f0-9]", "", $intgr);
   
$hex=ereg_replace("[^A-Fa-f0-9]", "", $hex);
   
$answer=0;
    for(
$i=0;$i < strlen($hex); $i++)
    {
       
$digit=hexdec(substr($hex,$i,1))/16;   // .f is 15/16 because in decimal .9 is 9/10
       
$answer += $digit/pow(16,$i);
    }
return
hexdec($intgr)+$answer;
}

echo
floatinghexdec("ff.ff");//255.99609375
?>
chuckySTAR
15-Apr-2009 08:55
Here's my hexdec function for greater numbers using BC Math

<?php
function bchexdec($hex)
{
   
$len = strlen($hex);
    for (
$i = 1; $i <= $len; $i++)
       
$dec = bcadd($dec, bcmul(strval(hexdec($hex[$i - 1])), bcpow('16', strval($len - $i))));
   
    return
$dec;
}

echo
bchexdec('ffffffffffffffffffffffffffffffff') . "\n" . (pow(2, 128));
?>
eds at edsavenue dot com
28-Mar-2009 12:13
I tried the example by joquius at kakugo dot com, but it didn't work.  i changed it to the following, which did work.

<?php
$str
= preg_replace_callback ("([a-zA-Z0-9]{2})", create_function ('$matches', 'return chr (hexdec ($matches[0]));'), $str);
?>
joquius at kakugo dot com
24-Sep-2008 01:12
Help a hex-stricken string get back to normal:

<?php
$str
= preg_replace_callback ("/%([a-zA-Z0-9]{2})/", create_function ('$matches', 'return chr (hexdec ($matches[1]));'), $str);
?>
this1is4me at hotmail dot com
27-May-2008 09:46
In reply to Amit Yadav's post (hex to binary conversion):

function binfromdec($num)
{
  $primary = "bit";
  for ($i=1; $i<=16; $i++)
    ${$primary.$i} = 0;
 
  if ($num & 32768)   $bit16  = 1;
  if ($num & 16384)   $bit15  = 1;
  if ($num & 8192)    $bit14  = 1;
  if ($num & 4096)    $bit13  = 1;
  if ($num & 2048)    $bit12  = 1;
  if ($num & 1024)    $bit11  = 1;
  if ($num & 512)     $bit10  = 1;
  if ($num & 256)     $bit9   = 1;
  if ($num & 128)     $bit8   = 1;
  if ($num & 64)      $bit7   = 1;
  if ($num & 32)      $bit6   = 1;
  if ($num & 16)      $bit5   = 1;
  if ($num & 8)       $bit4   = 1;
  if ($num & 4)       $bit3   = 1;
  if ($num & 2)       $bit2   = 1;
  if ($num & 1)       $bit1   = 1;
 
  return ($bit16. $bit15. $bit14. $bit13. $bit12. $bit11. $bit10. $bit9. $bit8. $bit7. $bit6. $bit5. $bit4. $bit3. $bit2. $bit1);
}
Walter Wlodarski
31-Jan-2008 09:33
One of my favourite, multi-purpose, bidirectional solution I wrote many years ago:

function bgr2rgb($cr) {  // bidirectional
    return (($cr & 0x0000FF) << 16 | ($cr & 0x00FF00) | ($cr & 0xFF0000) >> 16);
}

Which you might want to use as :

function hex2cr($hex) {  // strips any leading characters, like #
    return bgr2rgb(hexdec($hex));
}

function cr2hex($cr) { // the usual HTML format, #rrggbb
    return '#'.str_pad(strtoupper(dechex(bgr2rgb($cr))), 6, '0', STR_PAD_LEFT);
}

And, if like me you tend to mistype function names, the synonym :

function rgb2bgr($val) { return bgr2rgb($val); }
maddddidley at yahoo dot com
27-Jan-2008 08:17
Function that combines two rgb colors.

function combineColors($color1, $color2) {
       
        $color1 = str_replace("#", '', $color1);
        $color2 = str_replace("#", '', $color2);
       
        $r1 = hexdec(substr($color1, 0, 2));
        $g1 = hexdec(substr($color1, 2, 2));
        $b1 = hexdec(substr($color1, 4, 2));
       
        $r2 = hexdec(substr($color2, 0, 2));
        $g2 = hexdec(substr($color2, 2, 2));
        $b2 = hexdec(substr($color2, 4, 2));
       
        $r3 = ceil(($r1 + $r2) / 2);
        $g3 = ceil(($g1 + $g2) / 2);
        $b3 = ceil(($b1 + $b2) / 2);
       
       
        $color = rgbhex($r3, $g3, $b3);
        return $color = str_replace("#", '', $color);
       
    }
Anonymous
14-Nov-2007 04:34
// Fun√√_o GET Cor Hexadecima e Retorna em RGB
function hexrgb($hexstr, $rgb) {
 $int = hexdec($hexstr);
 switch($rgb) {
        case "r":
        return 0xFF & $int >> 0x10;
            break;
        case "g":
        return 0xFF & ($int >> 0x8);
            break;
        case "b":
        return 0xFF & $int;
            break;
        default:
        return array(
            "r" => 0xFF & $int >> 0x10,
            "g" => 0xFF & ($int >> 0x8),
            "b" => 0xFF & $int
            );
            break;
    }   
}// END GET Cor Hex => RGB

//Uso
 echo hexrgb("1a2b3c", r); // 26
 echo hexrgb("1a2b3c", g); // 43
 echo hexrgb("1a2b3c", b); // 60
//ou

var_dump(hexrgb("1a2b3c", rgb)); //array(3) { ["r"]=>  int(26) ["g"]=>  int(43) ["b"]=>  int(60) }
k10206 at naver dot com
27-Oct-2007 04:42
<?
function hexrgb($hexstr) {
   
$int = hexdec($hexstr);

    return array(
"red" => 0xFF & ($int >> 0x10), "green" => 0xFF & ($int >> 0x8), "blue" => 0xFF & $int);
}
?>
venk
16-Jun-2007 10:27
Reply To Halit Yesil's script:

Great Function!! But, there's a problem with your script if the user passes something with three letters/numbers (eg/ #000).  You need to use str_repeat to duplicate each character.

                if($l == 3){
                    unset($out);
                    $out[0] = $out['r'] = $out['red'] = hexdec(str_repeat(substr($c, 0,1),2));
                    $out[1] = $out['g'] = $out['green'] = hexdec(str_repeat(substr($c, 1,1),2));
                    $out[2] = $out['b'] = $out['blue'] = hexdec(str_repeat(substr($c, 2,1),2));
                }
Manithu
24-Mar-2007 12:23
This tiny function will return foreground colors (either black or white) in contrast to the color you provide:

<?php

function getContrastColor($color)
{
    return (
hexdec($color) > 0xffffff/2) ? '000000' : 'ffffff';
}

?>

This function will return the opposite (negative):

<?php

function negativeColor($color)
{
   
//get red, green and blue
   
$r = substr($color, 0, 2);
   
$g = substr($color, 2, 2);
   
$b = substr($color, 4, 2);
   
   
//revert them, they are decimal now
   
$r = 0xff-hexdec($r);
   
$g = 0xff-hexdec($g);
   
$b = 0xff-hexdec($b);
   
   
//now convert them to hex and return.
   
return dechex($r).dechex($g).dechex($b);
}

?>
Halit Yesil mail at halityesil dot com
22-Mar-2007 01:46
RGB to Hex
Hex to RGB
Function

<?PHP

function rgb2hex2rgb($c){
            if(!
$c) return false;
           
$c = trim($c);
           
$out = false;
            if(
eregi("^[0-9ABCDEFabcdef\#]+$", $c)){
               
$c = str_replace('#','', $c);
               
$l = strlen($c);
                if(
$l == 3){
                    unset(
$out);
                   
$out[0] = $out['r'] = $out['red'] = hexdec(substr($c, 0,1));
                   
$out[1] = $out['g'] = $out['green'] = hexdec(substr($c, 1,1));
                   
$out[2] = $out['b'] = $out['blue'] = hexdec(substr($c, 2,1));
                }elseif(
$l == 6){
                    unset(
$out);
                   
$out[0] = $out['r'] = $out['red'] = hexdec(substr($c, 0,2));
                   
$out[1] = $out['g'] = $out['green'] = hexdec(substr($c, 2,2));
                   
$out[2] = $out['b'] = $out['blue'] = hexdec(substr($c, 4,2));
                }else
$out = false;
               
            }elseif (
eregi("^[0-9]+(,| |.)+[0-9]+(,| |.)+[0-9]+$", $c)){
                if(
eregi(",", $c))
                   
$e = explode(",",$c);
                else if(
eregi(" ", $c))
                   
$e = explode(" ",$c);
                else if(
eregi(".", $c))
                   
$e = explode(".",$c);
                else return
false;
               
                if(
count($e) != 3) return false;
               
               
$out = '#';
                for(
$i = 0; $i<3; $i++)
                   
$e[$i] = dechex(($e[$i] <= 0)?0:(($e[$i] >= 255)?255:$e[$i]));
               
                for(
$i = 0; $i<3; $i++)
                   
$out .= ((strlen($e[$i]) < 2)?'0':'').$e[$i];
                   
               
$out = strtoupper($out);
            }else
$out = false;
           
            return
$out;
        }

        echo
'#FFFFFF => '.rgb2hex2rgb('#FFFFFF').'<br>';
        echo
'#FFCCEE => '.rgb2hex2rgb('#FFCCEE').'<br>';
        echo
'CC22FF => '.rgb2hex2rgb('CC22FF').'<br>';
        echo
'0 65 255 => '.rgb2hex2rgb('0 65 255').'<br>';
        echo
'255.150.3 => '.rgb2hex2rgb('255.150.3').'<br>';
        echo
'100,100,250 => '.rgb2hex2rgb('100,100,250').'<br>';

?>

Output

#FFFFFF =>
 Array{
   red=>255,
   green=>255,
   blue=>255,
   r=>255,
   g=>255,
   b=>255,
   0=>255,
   1=>255,
   2=>255
 }
 

#FFCCEE =>
 Array{
   red=>255,
   green=>204,
   blue=>238,
   r=>255,
   g=>204,
   b=>238,
   0=>255,
   1=>204,
   2=>238
 }
CC22FF =>
 Array{
   red=>204,
   green=>34,
   blue=>255,
   r=>204,
   g=>34,
   b=>255,
   0=>204,
   1=>34,
   2=>255
 }

0 65 255 => #0041FF
255.150.3 => #FF9603
100,100,250 => #6464FA
cgarvis at gmail dot com
09-Oct-2006 05:39
Here is my version of hex2rgb for web colors to 24bit colors.

<?php
function hex2rgb_webcolors($hex) {
   
$hex = eregi_replace("[^a-fA-F0-9]", "", $hex);
    switch(
strlen($hex) ) {
        case
2:
           
$hex = substr($hex,0,2)."0000";
            break;
        case
3:
           
$hex = substr($hex,0,1).substr($hex,0,1)
            .
substr($hex,1,1).substr($hex,1,1)
            .
substr($hex,2,1).substr($hex,2,1);
            break;
        case
4:
           
$hex = substr($hex,0,4)."00";
            break;
        case
6:
            break;
        default:
           
$hex = 0;
            break;
    }
    return
hexdec($hex);
}
?>
Lukasz (Zajonc) Zajaczkowski
18-Aug-2006 08:44
Function converting HEX to signed DEC

function hex2sdec ($hex)
{
  //how many bytes
  $ib = strlen ($hex) - (strlen ($hex) % $hex)) / $hex;
  if ((strlen ($hex) % 2) > 0)
    $ib = $ib + 1;

  //how many bites
  $ibb = 8 * $ib;

  //search for -1 value (max_uj)
  $buf = '1';
  for ($i = 1; $i <= $ibb - 1; $i++)
  {
    $buf .= '0';
  }
  $max_uj = bindec ($buf);

  //decide a sign, and calculate a value
  if (hexdec ($hex) < $max_uj)
  //+
  {
    $sdec = hexdec ($hex);
  }
  else
  //-
  {
    //search for max value + 1
    //(for ex. if hex = 23ef then max_p1 = ffff + 1)
    $buf = '';
    for ($i = 1; $i <= $ib; $i++)
    {
      $buf .= 'ff';
    }
    $max_p1 = hexdec ($buf) + 1;

    $sdec = hexdec ($hex) - $max_p1;
  }

  return $sdec;
}
repley at freemail dot it
29-May-2006 01:55
From color to color to ...... to color with fade effect. Good for dynamic bar chart.

<?php
//MultiColorFade(array hex-colors, int steps)
function MultiColorFade($hex_array, $steps) {

$tot = count($hex_array);
$gradient = array();
$fixend = 2;
$passages = $tot-1;
$stepsforpassage = floor($steps/$passages);
$stepsremain = $steps - ($stepsforpassage*$passages);

   for(
$pointer = 0; $pointer < $tot-1 ; $pointer++) {
 
      
$hexstart = $hex_array[$pointer];
      
$hexend = $hex_array[$pointer + 1];

       if(
$stepsremain > 0){
           if(
$stepsremain--){
              
$stepsforthis = $stepsforpassage + 1;
           }
       }else{
          
$stepsforthis = $stepsforpassage;
       }
   
       if(
$pointer > 0){
          
$fixend = 1;        
       }
   
      
$start['r'] = hexdec(substr($hexstart, 0, 2));
      
$start['g'] = hexdec(substr($hexstart, 2, 2));
      
$start['b'] = hexdec(substr($hexstart, 4, 2));

      
$end['r'] = hexdec(substr($hexend, 0, 2));
      
$end['g'] = hexdec(substr($hexend, 2, 2));
      
$end['b'] = hexdec(substr($hexend, 4, 2));
 
      
$step['r'] = ($start['r'] - $end['r']) / ($stepsforthis);
      
$step['g'] = ($start['g'] - $end['g']) / ($stepsforthis);
      
$step['b'] = ($start['b'] - $end['b']) / ($stepsforthis);
   
       for(
$i = 0; $i <= $stepsforthis-$fixend; $i++) {
 
          
$rgb['r'] = floor($start['r'] - ($step['r'] * $i));
          
$rgb['g'] = floor($start['g'] - ($step['g'] * $i));
          
$rgb['b'] = floor($start['b'] - ($step['b'] * $i));
 
          
$hex['r'] = sprintf('%02x', ($rgb['r']));
          
$hex['g'] = sprintf('%02x', ($rgb['g']));
          
$hex['b'] = sprintf('%02x', ($rgb['b']));
 
          
$gradient[] = strtoupper(implode(NULL, $hex));
       }
   }
 
  
$gradient[] = $hex_array[$tot-1];
 
return
$gradient;
}
//end MultiColorFade()

//start test
$multi_hex_array = array();
$multi_hex_array[] = array('FF0000','FFFF00');
$multi_hex_array[] = array('FF0000','FFFF00','00FF00');
$multi_hex_array[] = array('FF0000','FFFF00','00FF00','00FFFF');
$multi_hex_array[] = array('FF0000','FFFF00','00FF00','00FFFF','0000FF');
$multi_hex_array[] = array('FF0000','FFFF00','00FF00','00FFFF','0000FF','000000');
$multi_hex_array[] = array('FF0000','FFFF00','00FF00','00FFFF','0000FF','000000','FFFFFF');

foreach(
$multi_hex_array as $hex_array){

  
$totcolors = count($hex_array);
  
$steps = 44;

  
$a = MultiColorFade($hex_array, $steps);
  
$tot = count($a);

  
$table = '<table border=1 width="300">' . "\n";

   for (
$i = 0; $i < $tot; $i++){
      
$table .= ' <tr><td bgcolor="' . $a[$i] . '">' . ($i+1) .'</td><td><pre>' . $a[$i] . '</pre></td></tr>' . "\n";
   }
 
  
$table .= '</table><br /><br />';
 
   echo
'<br />Demanded steps = ' . $steps . '<br />';
   echo
'Returned steps = ' . $tot;
 
   if(
$steps == $tot){
       echo
'<br />OK.' . $steps . ' = ' . $tot . '<br />';
   }else{
       echo
'<br /><span style="color:#FF0000">FAILED! Demanded steps and returned steps are NOT equal!: ' . $steps . ' != ' . $tot . '</span><br />';
   }

   echo
$table;
 
}
//end test
?>

Repley.
greatwhitepine at NOSPAM dot yahoo dot ca
30-Mar-2006 08:46
Hex to binary conversion that works for large and small hex numbers.

<?php

function hexbin($str_hex) {
 
$str_bin = FALSE;
  for (
$i=0; $i < strlen($str_hex); $i++) {
   
$str_bin .= sprintf("%04s", decbin(hexdec($str_hex[$i])));
  }
  return
$str_bin;
}

$str_hex = "effffff20df";

print
"\n           HEX VALUE: $str_hex\n";
printf("   REAL BINARY VALUE: %50s\n", hexbin($str_hex));
printf("CHOPPED BINARY VALUE: %50s\n\n", decbin(hexdec($str_hex)));

?>
ayadav at infoprocorp dot com
28-Dec-2005 08:03
From Amit Yadav

Hex to binary conversion

$num = hexdec("20DF");
echo binfromdec($num);

function binfromdec($num)
{
    if ($num > 32766)    return ("Too Large!");
    if ($num & 16384)    $bit15 = 1;
    if ($num & 8192)    $bit14 = 1;
    if ($num & 4096)    $bit13 = 1;
    if ($num & 2048)    $bit12 = 1;
    if ($num & 1024)    $bit11 = 1;
    if ($num & 512)        $bit10 = 1;
    if ($num & 256)        $bit9 = 1;
    if ($num & 128)        $bit8 = 1;
    if ($num & 64)        $bit7 = 1;
    if ($num & 32)        $bit6 = 1;
    if ($num & 16)        $bit5 = 1;
    if ($num & 8)        $bit4 = 1;
    if ($num & 4)        $bit3 = 1;
    if ($num & 2)        $bit2 = 1;
    if ($num & 1)        $bit1 = 1;

    return ("" . $bit15 . $bit14 . $bit13 . $bit12 . $bit11 . $bit10 . $bit9 . $bit8 . $bit7 . $bit6 . $bit5 . $bit4 . $bit3 . $bit2 . $bit1);

}
cory at lavacube dot com
28-Oct-2005 08:59
A handy little function to convert HEX colour codes to "web safe" colours...

<?php

function color_mkwebsafe ( $in )
{
  
// put values into an easy-to-use array
  
$vals['r'] = hexdec( substr($in, 0, 2) );
  
$vals['g'] = hexdec( substr($in, 2, 2) );
  
$vals['b'] = hexdec( substr($in, 4, 2) );

  
// loop through
  
foreach( $vals as $val )
   {
      
// convert value
      
$val = ( round($val/51) * 51 );
      
// convert to HEX
      
$out .= str_pad(dechex($val), 2, '0', STR_PAD_LEFT);
   }

   return
$out;
}

?>

Example: color_mkwebsafe('0e5c94');
Produces: 006699

Hope this helps someone out... Happy coding. :-)
hajamie@home
24-Oct-2005 02:38
This function will take a hex $color, e.g. fa34bc and make it the shade you want, e.g. anywhere between 0 and 255. The smaller the number, the darker the output color.  It keeps the color the same, only changing the shade.  

function correctshade($color, $shade)
{
$r = hexdec(substr($color,0,2));
$g = hexdec(substr($color,2,2));
$b = hexdec(substr($color,4,2));
$sum = ($r + $g + $b);
$x = (($shade * 3) - $sum) / $sum;
if ($x >= 0) {
$x = $x + 1;
} else {
$x = 1 + $x;
}
$r = intval($x * $r);
$g = intval($x * $g);
$b = intval($x * $b);
$r = dechex($r);
$g = dechex($g);
$b = dechex($b);
return $r.$g.$b;
}
09-Oct-2005 05:53
I needed to get the opposite colors so my website would be soft on the eyes.

<?php
function OppositeHex($color)
{
$r = dechex(255 - hexdec(substr($color,0,2)));
$r = (strlen($r) > 1) ? $r : '0'.$r;
$g = dechex(255 - hexdec(substr($color,2,2)));
$g = (strlen($g) > 1) ? $g : '0'.$g;
$b = dechex(255 - hexdec(substr($color,4,2)));
$b = (strlen($b) > 1) ? $b : '0'.$b;
return
$r.$g.$b;
}

//Example
$color = '000000';
echo
'The opposite of #'.$color.' is #'.OppositeHex($color).';
?>
detrate at hotmail dot com
30-Sep-2005 01:38
I made this for a little phpbb mod.  It was used to take the hex value from the database and make a color 20 (in decimal) less, resulting a darker color.

EXAMPLE: #336699 to #1f5285

<?php

$row1
= "336699"; // color
$c = 20;          // difference value

$rgb = array(substr($row1,0,2), substr($row1,2,2), substr($row1,4,2));

for(
$i=0; $i < 3; $i++)
{
  if((
hexdec($rgb[$i])-$c) >= 0)
  {
  
$rgb[$i] = hexdec($rgb[$i])-$c;

  
$rgb[$i] = dechex($rgb[$i]);
    if(
hexdec($rgb[0]) <= 9)
    
$rgb[$i] = "0".$rgb[$i];
  } else {
   
$rgb[$i] = "00";
  }
}

$row2 = $rgb[0].$rgb[1].$rgb[2];

?>
Gabriel Reguly
16-Aug-2005 06:24
After esnhexdec from "rledger at gmail dot com",  the esndechex:

<?php
   
function esndechex($dec){
        
$a = strtoupper(dechex(substr($dec, 1 2)));
        
$b = strtoupper(dechex(substr($dec, 3, 10)));
         return
$a . $b;
    }
?>
djneoform at gmail dot com
20-Jun-2005 04:51
since i couldn't find one, here's an HEX to ASCII converter..

(takes HEX strings (in ASCII) and converts each two digit HEX code into it's ASCII equivalent)

function hex2ascii($str)
{
    $p = '';
    for ($i=0; $i < strlen($str); $i=$i+2)
    {
        $p .= chr(hexdec(substr($str, $i, 2)));
    }
    return $p;
}
bishop
05-Jun-2005 02:51
Bullet-proof hex-to-rgb colour converter like brian at sagesport dot com wanted, just far fewer code lines. As a bonus, gives you the ability to return as string or array:

<?php
   
function &hex2rgb($hex, $asString = true)
    {
       
// strip off any leading #
       
if (0 === strpos($hex, '#')) {
           
$hex = substr($hex, 1);
        } else if (
0 === strpos($hex, '&H')) {
           
$hex = substr($hex, 2);
        }      

       
// break into hex 3-tuple
       
$cutpoint = ceil(strlen($hex) / 2)-1;
       
$rgb = explode(':', wordwrap($hex, $cutpoint, ':', $cutpoint), 3);

       
// convert each tuple to decimal
       
$rgb[0] = (isset($rgb[0]) ? hexdec($rgb[0]) : 0);
       
$rgb[1] = (isset($rgb[1]) ? hexdec($rgb[1]) : 0);
       
$rgb[2] = (isset($rgb[2]) ? hexdec($rgb[2]) : 0);

        return (
$asString ? "{$rgb[0]} {$rgb[1]} {$rgb[2]}" : $rgb);
    }
?>

Handles 2, 3, and 6 character colour codes with leading # or &H.
Joey Morwick
02-May-2005 08:07
I found it helpful to have the inverse / reverse of this function laying around, since I wanted to insert some binary data into an xmlrpc call (it currently craps out when you do that), and I couldn't find one laying around, so here's a simple little function to do that:

function hex2bin($str) {
    $build = '';
    while(strlen($str) > 1) {
        $build .= chr(hexdec(substr($str, 0, 2)));
        $str = substr($str, 2, strlen($str)-2);
    }
    return $build;
}
rledger at gmail dot com
29-Mar-2005 07:59
To convert a cellular ESN from hexadecimal to decimal, use the following code. The base conversion is different due to the fact that the first two characters of a hexadecimal value must be converted seperately from the remaining six characters.
<?
function esnhexdec($hex){
  
$a = sprintf("%03d", hexdec(substr($hex, 0, 2)));
  
$b = sprintf("%08d", hexdec(substr($hex, 2, 6)));
   return
$a . $b;
}
?>
zubfatal, root at it dot dk
25-Mar-2005 10:36
This replaces my previous class.
I've added a few more input checks in the rgb2hex function.
Also it returned incorrect hex values for 1-digit values.

color::rgb2hex(array(0,0,0)) would output 000 not 00000.

<?php

/**
* Convert colors
*
* Usage:
*  color::hex2rgb("FFFFFF")
*  color::rgb2hex(array(171,37,37))
*
* @author      Tim Johannessen <root@it.dk>
* @version     1.0.1
*/

class color {

   
/**
     * Convert HEX colorcode to an array of colors.
     * @return      array        Returns the array of colors as array(red,green,blue)
     */
    
   
function hex2rgb($hexVal = "") {
       
$hexVal = eregi_replace("[^a-fA-F0-9]", "", $hexVal);
        if (
strlen($hexVal) != 6) { return "ERR: Incorrect colorcode, expecting 6 chars (a-f, 0-9)"; }
       
$arrTmp = explode(" ", chunk_split($hexVal, 2, " "));
       
$arrTmp = array_map("hexdec", $arrTmp);
        return array(
"red" => $arrTmp[0], "green" => $arrTmp[1], "blue" => $arrTmp[2]);
    }
    
   
/**
     * Convert RGB colors to HEX colorcode
     * @return      string        Returns the converted colors as a 6 digit colorcode
     */
   
function rgb2hex($arrColors = null) {
        if (!
is_array($arrColors)) { return "ERR: Invalid input, expecting an array of colors"; }
        if (
count($arrColors) < 3) { return "ERR: Invalid input, array too small (3)"; }
        
       
array_splice($arrColors, 3);
        
        for (
$x = 0; $x < count($arrColors); $x++) {
            if (
strlen($arrColors[$x]) < 1) {
                return
"ERR: One or more empty values found, expecting array with 3 values";
            }
            
            elseif (
eregi("[^0-9]", $arrColors[$x])) {
                return
"ERR: One or more non-numeric values found.";
            }
            
            else {
                if ((
intval($arrColors[$x]) < 0) || (intval($arrColors[$x]) > 255)) {
                    return
"ERR: Range mismatch in one or more values (0-255)";
                }
                
                else {
                   
$arrColors[$x] = strtoupper(str_pad(dechex($arrColors[$x]), 2, 0, STR_PAD_LEFT));
                }
            }
        }
        
        return
implode("", $arrColors);
    }

}

?>
brian at sagesport dot com
22-Mar-2005 05:08
The issue I've seen with the existing hex to dec conversion routines is the lack of error-trapping.  I stick to the theory that one should try to cover ALL the bases when writing a generalized routine such as this one.  I have a varied background that covers a wide variety of design/development languages, on the web as well as desktop apps.  As such I've seen multiple formats for writing hex colors.

For example, the color red COULD be written as follows:
#ff0000
&Hff0000
#ff
&Hff

Therefore I have written a function that is case-insensitive and takes into account the chance that different developers have a tendency to format hex colors in different ways.

<?php
 
function convert_color($hex){
   
$len = strlen($hex);
   
$chars = array("#","&","H","h");
   
$hex = strip_chars($hex, $chars);
   
preg_match("/([0-9]|[A-F]|[a-f]){".$len."}/i",$hex,$arr);
   
$hex = $arr[0];
    if (
$hex) {
      switch(
$len) {
        case
2:
         
$red = hexdec($hex);
         
$green = 0;
         
$blue = 0;
          break;
        case
4:
         
$red = hexdec(substr($hex,0,2));
         
$green=hexdec(substr($hex,2,2));
         
$blue = 0;
          break;
        case
6:
         
$red = hexdec(substr($hex,0,2));
         
$green=hexdec(substr($hex,2,2));
         
$blue = hexdec(substr($hex,4,2));
          break;      
      };
     
$color[success] = true;
     
$color[r] = $red;
     
$color[g] = $green;
     
$color[b] = $blue;
      return
$color;
    } else {
     
$color[success] = false;
     
$color[error] = "unable to convert hex to dec";
    };
  }

  function
strip_chars($string, $char){
   
$len = strlen($string);
   
$count = count($char);
    if (
$count >= 2) {
      for (
$i=0;$i<=$count;$i++) {
        if (
$char[$i]) {
         
$found = stristr($string,$char[$i]);
          if (
$found) {
           
$val = substr($string,$found+1,$len-1);
           
$string = $val;
          };
        };
      };
    } else {
     
$found = stristr($string,$char);
      if (
$found) {
       
$val = substr($string,$found+1,$len-1);
      };
    };
    echo
$val;
    return
$val;
  }

 
/*
    To use simply use the following function call:
      $color = convert_color("#FF");
      this will return the following assoc array if successful:
      *[success] = true
      *[r] = 255
      *[g] = 0
      *[b] = 0

      or copy and paste the following code:
     
      $hex = "FFFFFF"; // Color White
      $color = convert_color($hex);
      var_dump($color);
 */
?>

As you can see, the function "convert_color" accepts a hex # in most acceptable formats and returns an associative array.  [success] is set to TRUE if the function succeeds and FALSE if not.  The array members [r], [g] and [b] hold the red,green and blue values respectively.  If it fails, [error] holds a custom error message.

"strip_chars" is a support function written to remove the unwanted characters from the hex string, and sends the concatenated string back to the calling function.  It will accept either a single value or an array of values for the characters to remove.
groobo
10-Feb-2005 07:46
It's just a revision to marfastic's ligten_up script, it simply adds/subtracts mod_color to orig_color.
I use it often to adjust tonals rather than brightness only

<?
function mod_color($orig_color, $mod, $mod_color){
   
/*
        $orig_color - original html color, hex
        $mod_color - modifying color, hex
        $mod - modifier '+' or '-'
        usage: mod_color('CCCCCC', '+', '000033')
    */
    // does quick validation
   
preg_match("/([0-9]|[A-F]){6}/i",$orig_color,$orig_arr);
   
preg_match("/([0-9]|[A-F]){6}/i",$mod_color,$mod_arr);
    if (
$orig_arr[0] && $mod_arr[0]) {
        for (
$i=0; $i<6; $i=$i+2) {
           
$orig_x = substr($orig_arr[0],$i,2);
           
$mod_x = substr($mod_arr[0],$i,2);
            if (
$mod == '+') { $new_x = hexdec($orig_x) + hexdec($mod_x); }
            else {
$new_x = hexdec($orig_x) - hexdec($mod_x); }
            if (
$new_x < 0) { $new_x = 0; }
            else if (
$new_x > 255) { $new_x = 255; };
           
$new_x = dechex($new_x);
           
$ret .= $new_x;
        }
        return
$ret;
    } else { return
false; }
}
?>
19-Jan-2005 05:33
I wondered long time what is the best way to generate RGB-color from HEX-color, and just now i found the simpliest way!

<?php
$hex
= "FF00FF";
$rgb = hexdec($hex); // 16711935
?>

I hope this will save your time! :)
marfastic
10-Dec-2004 03:14
Here is a function to brighten up any color:

function lighten_up($orig_color, $fraction_denom){
            // return the color between the color and white
            // based on the fraction denom that is passed
           
            if(!isset($fraction_denom))
                $fraction_denom = 2;
            $highest_val = hexdec("FF");
            $r = hexdec(substr($orig_color,0,2));
            $r = ($highest_val-$r)/$fraction_denom + $r;
            $g = hexdec(substr($orig_color,2,2));
            $g = ($highest_val-$g)/$fraction_denom + $g;
            $b = hexdec(substr($orig_color,4,2));
            $b = ($highest_val-$b)/$fraction_denom + $b;
            return dechex($r) . dechex($g) . dechex($b);
        }
_meto ALT+q web.de
08-May-2004 04:00
Damn, this took me some real long time! Maybe it's helpfull for those who even have no idea of color-Schemes like me ;)

If u want to generate PDF's for Print Offices u need to set all the colors in CMYK.

Here is a Function that will convert RGB to CMYK

<?
function hex2rgb($hex) {
 
$color = str_replace('#','',$hex);
 
$rgb = array('r' => hexdec(substr($color,0,2)),
              
'g' => hexdec(substr($color,2,2)),
              
'b' => hexdec(substr($color,4,2)));
  return
$rgb;
}

function
rgb2cmyk($var1,$g=0,$b=0) {
   if(
is_array($var1)) {
     
$r = $var1['r'];
     
$g = $var1['g'];
     
$b = $var1['b'];
   }
   else
$r=$var1;
  
$cyan    = 255 - $r;
  
$magenta = 255 - $g;
  
$yellow  = 255 - $b;
  
$black   = min($cyan, $magenta, $yellow);
  
$cyan    = @(($cyan    - $black) / (255 - $black)) * 255;
  
$magenta = @(($magenta - $black) / (255 - $black)) * 255;
  
$yellow  = @(($yellow  - $black) / (255 - $black)) * 255;
   return array(
'c' => $cyan / 255,
               
'm' => $magenta / 255,
               
'y' => $yellow / 255,
               
'k' => $black / 255);
}

$color=rgb2cmyk(hex2rgb('#FF0000'));
pdf_setcolor($pdf, "both", "cmyk", $color['c'], $color['m'], $color['y'], $color['k']);
?>

U can call it with parameters (r,g,b) or just with an array(r,g,b) that contains these values.

Hope it works correct. All testing was fine.
gelado at ip3 dot com
29-Aug-2003 11:30
Another hex to decimal converter, up to the precision of PHP floats.

function longhex($hex)
{
    $dec = 0;
    $bitval = 1;
    for($pos = 1; $pos <= strlen($hex); $pos++) {
        $dec += hexdec(substr($hex, -$pos, 1)) * $bitval;
        $bitval *= 16;
    }
    return($dec);
}
henrique at recidive dot com
27-May-2003 10:43
Function to convert a string with hexadecimal colors to an associative array with RGB values:

<?
function hex2dec($hex) {
 
$color = str_replace('#', '', $hex);
 
$ret = array(
   
'r' => hexdec(substr($color, 0, 2)),
   
'g' => hexdec(substr($color, 2, 2)),
   
'b' => hexdec(substr($color, 4, 2))
  );
  return
$ret;
}

/*** Example:
print_r(hex2dec('3D58BE'));

or

print_r(hex2dec('#3D58BE'));

will return

Array
(
  [r] => 61
  [g] => 88
  [b] => 190
)
***/
?>

Thanks !

Henrique Recidive
andreas.schmeiler
05-Feb-2003 01:59
Here's another hex2bin variant, works pretty well to me.

function hex2bin($hexdata) {
  
   for ($i=0;$i<strlen($hexdata);$i+=2) {
      $bindata.=chr(hexdec(substr($hexdata,$i,2)));
   }
  
   return $bindata;
}
chrism at four dot net
15-Dec-2001 06:02
hexdec from 4.1.0 onwards does not show
the same size limitation and therefore
works differently with large numbers than previous php versions.

To obtain the same results, use:

(int) hexdec (...)
andychase at yahoo dot com
18-Jan-2001 02:32
For hex numbers larger than 7FFFFFFF (E.G. PalmOS dates in seconds elapsed since 01/01/1904), I came up with this:

<?php
function bighexdec($hexnumber){

   
$numlength = strlen($hexnumber);

   
$decnumber = 0;

    for(
$x = 1; $x <= $numlength; $x++){

       
$place = $numlength - $x;
       
       
$operand = hexdec(substr($hexnumber,$place,1));
           
       
$exponent = pow(16,$x-1);

       
$decValue = $operand * $exponent;
   
       
$decnumber += $decValue;

    }
    return
$decnumber;
}
?>
 

 
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