Math 函数
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PHP手册

dechex

(PHP 4, PHP 5)

dechex — 十进制转换为十六进制

说明

string dechex ( int $number )

返回一字符串，包含有给定 number 参数的十六进制表示。所能转换的最大数值为十进制的 4294967295，其结果为 "ffffffff"。

Example #1 dechex() 范例

<?php
echo dechex(10) . "\n";
echo dechex(47);
?>

以上例程会输出：

a
2f

参见 hexdec()，decbin()，decoct() 和 base_convert().。

参数

number

Decimal value to convert

返回值

Hexadecimal string representation of number

范例

Example #2 dechex() example

<?php
echo dechex(10) . "\n";
echo dechex(47);
?>

以上例程会输出：

a
2f

参见

Math 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 十进制转换为十六进制

用户评论:

sneskid at hotmail dot com (23-Mar-2012 03:09)

If you want to create or parse signed Hex values:

<?php
// $d should be an int
function sdechex($d) { return ($d<0) ? ('-' . dechex(-$d)) : dechex($d); }

// $h should be a string
function shexdec($h) { return ($h[0] === '-') ? -('0x' . substr($h,1) + 0) : ('0x' . $h + 0); }

// test

$v = sdechex(-123); // string(3) "-7b"
$i = shexdec($v);   // int(-123)
var_dump($v, $i);
?>

Also note that ('0x' . $str + 0) is faster than hexdec()

andries at centim dot be (07-Mar-2012 10:44)

If you need to convert a large number (> PHP_MAX_INT) to a hex value, simply use base_convert. For example:

base_convert('2190964402', 10, 16); // 829776b2

9381904 at gmail dot com (02-Nov-2011 06:11)

for mac address
<?php
function dec2mac($mac) {
   $mac=preg_split("([.])", $mac, 6);
   $hexmac="";
   foreach ($mac as $part)
   {
   $part=dechex($part);
   strlen($part)<2 ? $hexmac.="0$part" : $hexmac.=$part;
   }
   return $hexmac;
}
echo dec2mac("0.29.96.71.60.137"); // 001d60473c89
?>

Rod (13-Jan-2011 12:50)

After numerous hours of trying to actually receive a hexadecimal digit from dechex, I decided to give it a go myself.

I kept trying to do bitwise comparisons on the result however I was comparing strings,

<?php
function dectohex($dec){
   $code='return 0x'.dechex($dec).';';
   return eval($code);
}
?>

This actually returns a hexadecimal value, not a string representation.

Hopefully this saves someone else a couple of hours.

jpfstange at gmail dot com (02-Sep-2010 04:33)

<?php

        /**
        * String to HEX | HEX to String. Automatic detection.
        * This script just takes input from the command line
        * and transforms an ASCII String to HEX or viceversa.
        * If you want to use it in a web page just change the $str variable below.
        * Cheers, Juan Stange.-
        */

        $str = $_SERVER["argv"][1];

        function hexEncode($str=NULL){

                if(is_null($str)){
                        return FALSE;
                }

                $hexStr = "";

                for($i=0;isset($str[$i]);$i++){
                        $char = dechex(ord($str[$i]));
                        $hexStr .= $char;
                }

                return "0x".$hexStr;

        }

        function asciiEncode($str=NULL){

                if(!preg_match("/^0x[A-Fa-f0-9]+/",$str)){
                        return FALSE;   //Not a hex string
                }

                $str = substr($str,2);
                $asciiString = "";

                for($i=0;isset($str[$i]);$i+=2){
                        $hexChar = substr($str,$i,2);
                        $asciiString .= chr(hexdec($hexChar));
                }

                return $asciiString;

        }

        $return = ($encoded=asciiEncode($str)) ? $encoded : hexEncode($str);

        echo $return."\n";

?>

jbleau at gmail dot com (29-Oct-2008 10:23)

I was confused by dechex's size limitation. Here is my solution to the problem. It supports much bigger values, as well as signs.

<?php
function dec_to_hex($dec)
{
    $sign = ""; // suppress errors
    if( $dec < 0){ $sign = "-"; $dec = abs($dec); }

    $hex = Array( 0 => 0, 1 => 1, 2 => 2, 3 => 3, 4 => 4, 5 => 5,
                  6 => 6, 7 => 7, 8 => 8, 9 => 9, 10 => 'a',
                  11 => 'b', 12 => 'c', 13 => 'd', 14 => 'e',   
                  15 => 'f' );
       
    do
    {
        $h = $hex[($dec%16)] . $h;
        $dec /= 16;
    }
    while( $dec >= 1 );
   
    return $sign . $h;
}
?>

mountarreat at gmail dot com (11-May-2008 05:55)

I was challenged by a problem with large number calculations and conversion to hex within php. The calculation exceeded unsigned integer and even float range. You can easily change it for your needs but it is, thanks to bcmath, capable of handling big numbers via string. This function will convert them to hex.

In this specific example though, since I use it for game internals that can only handle 32 bit numbers, it will truncate calculations at 8 digits. If the input is 1 for example it will be filled up with zeros. Output 00000001h.

Of course I don't claim it to be a good one, but it works for me and my purpose. Suggestions on faster code welcome!

<?php
// Turns numbers into 32-bit hex string; Fills up zeros
function lrgDec2Hex($number)
{
    $i = 0;
    $hex = array();

    while($i < 8) {
        if($number == 0) {
            array_push($hex, '0');
        }
        else {
            array_push($hex, strtoupper(dechex(bcmod($number, '16'))));
            $number = bcdiv($number, '16', 0);
        }
        $i++;
    }
    krsort($hex);
    return implode($hex);
}
?>

sjaak at spoilerfreaks dot com (09-Mar-2007 03:28)

To force the correct usage of 32-bit unsigned integer in some functions, just add '+0'  just before processing them.

for example
<?php echo(dechex("2724838310")); ?>
will print '7FFFFFFF'
but it should print 'A269BBA6'

When adding '+0' php will handle the 32bit unsigned integer
correctly
<?php echo(dechex("2724838310"+0)); ?>
will print 'A269BBA6'

brent (16-Dec-2006 07:33)

Be very careful calling dechex on a number if it's stored in a string.

For instance:

The max number it can handle is 4294967295 which in hex is FFFFFFFF, as it says in the documentation.

dechex(4294967295) => FFFFFFFF //CORRECT

BUT, if you call it on a string of a number, it casts to int, and automatically gives you the largest int it can handle.

dechex('4294967295') => 7FFFFFFF //WRONG!

so you'll need to cast to a float:

dechex((float) '4294967295') => FFFFFFFF //CORRECT

This took me FOREVER to figure out, so hopefully I just saved someone some time.

foros at basnek dot com (24-Jul-2006 05:13)

I leave code blocks them that I have made to be able to replace the content of certain blocks of JS that used eval () I hope serves to them.

<?php
// Convert hex 2 str
// Imput Example: \x68\x6f\x6c\x61\x20\x6d\x75\x6e\x64\x6f
$que=( isset( $_POST['hexadecimal'] ) )?$_POST['hexadecimal']:"";
$valores=explode( "\\\x", $que );
for ( $i=0; $i<count( $valores ) ; $i++) {
    echo chr(  hexdec( $valores[$i] ) ) ;
}

// Convert str 2 hex
// Imput Example: hola mundo
$que=( isset( $_POST['ascii'] ) )?$_POST['ascii']:"";
for ( $i=0; $i<strlen( $que ) ; $i++) {
    echo "\\x".dechex( ord( substr( $que, $i, 1) ) ) ;
}
?>

Mista-NiceGuy at web dot de (28-Dec-2005 01:00)

These are functions to convert roman numbers (e.g. MXC) into dec and vice versa.
Note: romdec() does not check whether a string is really roman or not. To force a user-input into a real roman number use decrom(romdec($input)). This will turn XXXX into XL for example.

<?php
    function decrom($dec){
        $digits=array(
            1 => "I",
            4 => "IV",
            5 => "V",
            9 => "IX",
            10 => "X",
            40 => "XL",
            50 => "L",
            90 => "XC",
            100 => "C",
            400 => "CD",
            500 => "D",
            900 => "CM",
            1000 => "M"
        );
        krsort($digits);
        $retval="";
        foreach($digits as $key => $value){
            while($dec>=$key){
                $dec-=$key;
                $retval.=$value;
            }
        }
        return $retval;
    }

    function romdec($rom){
        $digits=array(
            "I" => 1,
            "V" => 5,
            "X" => 10,
            "L" => 50,
            "C" => 100,
            "D" => 500,
            "M" => 1000
        );
        $retval="";
        $chars=array();
        for($i=1;$i<=strlen($rom);$i++){
            $chars[]=substr($rom,$i-1,1);
        }
        $step=1;
        for($i=count($chars)-1;$i>=0;$i--){
            if(!isset($digits[$chars[$i]])){ return "Error!"; }
            if($step<=$digits[$chars[$i]]){
                $step=$digits[$chars[$i]];
                $retval+=$digits[$chars[$i]];
            }
            else{
                $retval-=$digits[$chars[$i]];
            }
        }
        return $retval;
    }

    echo decrom(romdec("XXXX"));
?>

cory at lavacube dot com (28-Oct-2005 12:45)

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. :-)

michael at m-ganzer dot de (18-Jul-2005 02:58)

simple, non-recursive way of zerofilling (why making everything complicated, there r more than enough inbuilt functions)

function zfill($n,$a) {
  return str_repeat("0",max(0,$a-strlen($n))).$n;
}

"max(0,..." as multiplier inside of "str-repeat" is preventing an error with negative values, if the string length was already higher than the accuracy parameter for zfill.

have fun! :)

trance4rm (17-Jul-2005 09:08)

a bugfix for admin AT bobfrank DOT org' s post

The original was:
<?php
function zeropad($num, $lim)
{
   return (strlen($num) >= $lim) ? $num : zeropad("0" . $num);
}
?>

I couldn't get it to work, kept getting a "Missing argument 2 for zeropad()" error, even though I called the function with both arguments -- then I noticed the recursive part, and the missing $lim argument.  The code that works is:

<?php
function zeropad($num, $lim)
{
   return (strlen($num) >= $lim) ? $num : zeropad("0" . $num, $lim);     // $lim was missing from the recursive call

// the function will prefix $num with a zero and recursively call itself
// each recursive call, $num gets one digit bigger until strlen of $num  equals $lim
}
?>

oliver at realtsp dot com (14-Jun-2005 09:46)

Warning for use on 64 bit machines! The Extra length matters!

32bit machine:
php -r 'echo dechex(4294967295);'
output: ffffffff

64bit machine:
php -r 'echo dechex(4294967295);'
output: ffffffff

so far it is ok. But for slightly bigger numbers:

32bit machine:
php -r 'echo dechex(4294967296);'
output: 0

64bit machine:
php -r 'echo dechex(4294967296);'
output: 100000000

note the difference!

This is particularly important when converting negative numbers:

64bit machine:
php -r 'echo dechex(-1);'
output: ffffffffffffffff

32bit machine:
php -r 'echo dechex(-1);'
output: ffffffff

If you want your code to be portable to amd64 or xeons (which are now quite popular with hosting companies) then you must ensure that your code copes with the different length of the result for negative numbers (and the max value, although that is probably less critical).

jrisken at mn dot rr dot com (29-May-2005 03:33)

A less elegant but (perhaps) faster way to pad is with substr with a negative length argument. I use it in this tiny function which formats computed rgb color codes for style sheets:
<?
function toColor($n)
{
return("#".substr("000000".dechex($n),-6));
}
?>

admin AT bobfrank DOT org (02-May-2005 03:28)

Here is a very small zeropadding that you can use for numbers:

function zeropad($num, $lim)
{
   return (strlen($num) >= $lim) ? $num : zeropad("0" . $num);
}

zeropad("234",6);

will produce:
000234

zeropad("234",1);

will produce:
234

matt dot smith at email dot ky (21-Apr-2005 05:14)

It took me hours, but I've finally figured it all out...

--
To figure up how many lines it'll take to get from,
0000 to FFFF, use this formula:
((hex_length / 2) * 255) + 1

For 0000 to FFFF, this would be: ((4 / 2) * 255) + 1 = 511
For 0000000000 to FFFFFFFFFF, this would be: ((10 / 2) * 255) + 1 = 1276

--
To figure up how many possibilities a certain hex length will give (such as that of an MD5 hash, for example), use this formula:
256^(hex_length / 2)

Like so:
hex = 0123ABCDEF
hex_length = 10
possibilities = 256^(10 / 2)
possibilities = 256^5
possibilities = 1,099,511,627,776

--
And I don't know how useful this next part is, but it's quite nifty. Just set $length to be your hex_length and it'll display all "incrementally-possible" hexadecimals, along with line numbers:

<?php
$length = 10; // Change this to the total length of your hexadecimal

function array_check($array1, $array2)
{
    $count1 = count($array1);
    $count2 = count($array2);
   
    if ($count1 != $count2)
        return FALSE;
   
    $match = 0;
    for ($i = 0; $i < $count1; $i++)
        if ($array1[$i] == $array2[$i])
            $match++;
   
    if ($match != $count1)
        return FALSE;
   
    return TRUE;
}

function zeropad($num)
{
    return (strlen($num) == 1) ? '0'.$num : $num;
}

function zeropad_lineno($num, $length)
{
    while (strlen($num) < $length)
        $num = '0'.$num;
   
    return $num;
}

$hexadecimals = $length / 2;
$possibilities = /*number_format(*/ pow(256, $hexadecimals) /*)*/;

echo "A hexadecimal of this length ({$length}) has {$possibilities} possibilities.<br>\n";
echo "<br>\n";

//init
for ($i = 0; $i < $hexadecimals; $i++)
{
    $x[] = '00';
    $xint[] = 0;
   
    $end[] = 'ff';
}

$line = 0;
while ( !(array_check($x, $end)) ) // while we're not currently at the end (FF..)
{
    $hexstr = '';
    for ($i = 0; $i < $hexadecimals; $i++)
    {
        $x[$i] = dechex($xint[$i]);
        $hexstr .= zeropad(dechex($xint[$i]));
    }
   
    $line++;
    $linestr = zeropad_lineno($line, 8);
    echo "<code>{$linestr}: {$hexstr}</code><br>\n";
   
    // hex increment
    for ($i = ($hexadecimals - 1); $i >= 0; $i--)
    {
        // increment bit if possible
        if ($xint[$i] != 255)
        {
            // increment bit and then break out of the for loop
            $xint[$i]++;
            break;
        }
    }
}
?>

manithu (29-Mar-2005 08:18)

If you want to fade some text from one color to another, use this function:

<?php

function colorFade($text, $color1, $color2, $HTMLelement = 'span')
{
    //remove leading and trailing whitespaces.
    $text = trim($text);
   
    //split the characters of the text to an array.
    $char = array();
    for ($i = 0; $i < strlen($text); $i++) {
        $char[$i] = substr($text, $i, 1);
    }
    //convert the hexadecimal colors in decimal.
    $decimalColor = array();
    //first color
    $decimalColor[0] = hexdec(substr($color1, 0, 2));
    $decimalColor[1] = hexdec(substr($color1, 2, 2));
    $decimalColor[2] = hexdec(substr($color1, 4, 2));
    //second color
    $decimalColor[3] = hexdec(substr($color2, 0, 2));
    $decimalColor[4] = hexdec(substr($color2, 2, 2));
    $decimalColor[5] = hexdec(substr($color2, 4, 2));
   
    //formated chars are stored here (the key 0 is for the first
    //char and must not be removed).
    $newText = array(0 => null);
    //run over every character except the first and the last,
    //they will be added later.
    for ($i = 2; $i <= strlen($text)-1; $i++) {
        //check if the character is only a whitespace. If yes,
        //save the whitespace without adding color and proceed
        //to the next character.
        if (!trim($char[$i-1])) {
            $newText[] = $char[$i-1];
            continue;
        }
        //calculate the (hex) color for this character.
        $color = array();
        //red
        $color[] = dechex(($decimalColor[0] - $decimalColor[3])
                   / strlen($text) * $i + $decimalColor[3]);
        //green
        $color[] = dechex(($decimalColor[1] - $decimalColor[4])
                   / strlen($text) * $i + $decimalColor[4]);
        //blue
        $color[] = dechex(($decimalColor[2] - $decimalColor[5])
                   / strlen($text) * $i + $decimalColor[5]);
       
        //check if every color part is 2 chars long, if not, repeat it.
        foreach ($color as $k => $v) {
            if (strlen($v) < 2) {
                $color[$k] = str_repeat($v, 2);
            }
        }
        //merge the parts to the full hex color.
        $color = implode($color, '');
       
        //Save the formated char.
        $newText[] = '<'.$HTMLelement.' style="color:#'.$color.'">'.
                     $char[$i-1].'</'.$HTMLelement.'>';
    }
    //add first char.
    $newText[0] = '<'.$HTMLelement.' style="color:#'.$color2.'">'.
                  $char[0].'</'.$HTMLelement.'>';
    //add last char.
    $newText[]  = '<'.$HTMLelement.' style="color:#'.$color1.'">'.
                  $char[strlen($text)-1].'</'.$HTMLelement.'>';
   
    //merge the characters and return it.
    return implode($newText, '');
}

?>

$color1 is the start color, $color2 the end color.

I hope this helps somebody.

morten at nilsen dot com (02-Jan-2005 12:30)

I see a lot of less-than-optimal functions posted on this page, so I feel I have to give some better examples...
due to the sheer size of this collection, I have made it available on my server, rather than copy/paste it into these comments.

http://ryo-ohki.4th-age.com/demos/able.php
and
http://ryo-ohki.4th-age.com/demos/able.phps

dechex replacement function from above source:
<?php
  define('BIT_BYTE', 8); // bits per byte
  define('HEX_BYTE', BIT_BYTE/4); // hex digits in a byte

  define('BIT_INT',  32); // sizeof(int)
  define('HEX_INT',  BIT_INT / (BIT_BYTE/HEX_BYTE)); // hex digits in an int

  function i2h($int, $group=HEX_BYTE, $size=HEX_INT, $sep=' ') {
    $ret = '';
    while($size--) {
      $n=($int>>($size*4)) & 0xf;
      $ret .= $n>9?chr(55 + $n):$n;
      if($size && $size%$group == 0) $ret .= $sep;
    }
    return $ret;
  }

  echo i2h(rand(1,2)==1?-mt_rand():mt_rand());
?>

wangster at darkcore dot net (15-Dec-2004 07:36)

This function will take a string and convert it into a hexdump.

e.g.

3c666f6e 74207369 7a653d22 33223e4c  <font.size."3">L
6561726e 20686f77 20746f20 62652061  earn.how.to.be.a

function hexdump($string) {
   $hex="";
   $substr = "";
   for ($i=0; $i < strlen($string) ;$i++) {
     if(!($i % 4) && $i != 0) {
       $hex .= " ";
     }
     if(!($i % 16) && $i != 0) {
       $clean = preg_replace("/[^a-zA-Z0-9!-.<>\/]/",".",$substr);
       $hex .= " ".htmlentities($clean)."\n";
       $substr = "";
     }
     $substr .=  $string[$i];
     $hex .= dechex(ord($string[$i]));
   }
   return $hex;
}

(12-Dec-2004 03:31)

If you need to generate random HEX-color, use this:
<?php
function random_hex_color(){
    return sprintf("%02X%02X%02X", mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));
}
$hex = random_hex_color(); // 09B826
?>

Enjoy.

(11-Dec-2004 09:30)

If you need to convert RGB-color into HEX-color, use this:
<?php
function rgb2hex($rgb){
    return sprintf("%06X", $rgb);
}
$hex = rgb2hex(65280); // 00FF00
?>

Ruben Barkow ( at web dot de) (24-May-2004 07:46)

this function generates an hex-colorcode out of a string.
usefull if you want to show a list of words all in different colors, that should remain its color even if the order changes.
(if the string is empty, it gives back a random color)

function word2color($w){
if (strlen($w)==0) return substr('00000' . dechex(mt_rand(0, 0xffffff)), -6);
while (strlen($w)<6) $w.=$w;
$minbrightness=1;  // range from 0 to 15, if this is 0 then for ex. black is allowed
$max_brightness=14; // range from 0 to 15, if this is 15 then for ex. white is allowed
$plus_red=0;    // set one of these to set the probability of one of these colors higher
$plus_green=0;
$plus_blue=0;
for ($i=0; $i<6; $i++) {
    #$r.= '">';// this is a depug mode, to see the color written
    $plus=0;
    if ($plus_red<>0 and $i==0) $plus=$plus_red;
    if ($plus_green<>0 and $i==2) $plus=$plus_green;
    if ($plus_blue<>0 and $i==4) $plus=$plus_blue;
    $c=$w[round(strlen($w)/6*$i)];
    $dec=ord($c)%($max_brightness+$plus-$minbrightness) +$minbrightness+$plus;
    if ($dec>$max_brightness-$minbrightness) $dec=$max_brightness-$minbrightness;
    $r.= strtoupper( dechex($dec) );
}
return $r;
}

admin[TAKETHISOUT] at torsoft dot no-ip dot com (21-Apr-2004 08:01)

<?php
/*
here are two functions, some might find them useful (maybe for encoding)
converting string to hex and hex to string:
*/

function strhex($string)
{
    $hex="";
    for ($i=0;$i<strlen($string);$i++)
        $hex.=(strlen(dechex(ord($string[$i])))<2)? "0".dechex(ord($string[$i])): dechex(ord($string[$i]));
    return $hex;
}
function hexstr($hex)
{
    $string="";
    for ($i=0;$i<strlen($hex)-1;$i+=2)
        $string.=chr(hexdec($hex[$i].$hex[$i+1]));
    return $string;
}
?>

daevid at daevid dot com (18-Mar-2004 10:59)

Here's my version of a red->yellow->green gradient:

<?php
function colorMeter($percent, $invert = false)
{
    //$percent is in the range 0.0 <= percent <= 1.0
    //    integers are assumed to be 0% - 100%
             // and are converted to a float 0.0 - 1.0
    //     0.0 = red, 0.5 = yellow, 1.0 = green
    //$invert will make the color scale reversed
    //     0.0 = green, 0.5 = yellow, 1.0 = red
   
    //convert (int)% values to (float)
    if (is_int($percent)) $percent = $percent * 0.01;
   
    $R = min((2.0 * (1.0-$percent)), 1.0) * 255.0;
    $G = min((2.0 * $percent), 1.0) * 255.0;
    $B = 0.0;
   
    return (($invert) ?
sprintf("%02X%02X%02X",$G,$R,$B)
: sprintf("%02X%02X%02X",$R,$G,$B));
} //colorMeter
?>

and use it like this:

<TABLE BORDER=1 WIDTH="300">
<?php
for ($i = 0.0; $i <= 1.0; $i += 0.10)
{
    $RGB = colorMeter($i);
    print "<TR><TD BGCOLOR='".$RGB."'>".$i."</TD><TD>
<PRE>".$RGB."</PRE></TD></TR>\n";
}
?>
</TABLE>

<P>

<TABLE BORDER=1 WIDTH="300">
<?php
for ($i = 0; $i <= 100; $i += 10)
{
    $RGB = colorMeter(intval($i), true);
    print "<TR><TD BGCOLOR='".$RGB."'>".$i."</TD><TD>
<PRE>".$RGB."</PRE></TD></TR>\n";
}
?>
</TABLE>

thr at recide dot net (10-Feb-2004 12:39)

/*
* RGB-Colorcodes(i.e: 255 0 255) to HEX-Colorcodes (i.e: FF00FF)
*/
function rgb2hex($rgb){
    if(!is_array($rgb) || count($rgb) != 3){
        echo "Argument must be an array with 3 integer elements";
        return false;
    }
    for($i=0;$i<count($rgb);$i++){
        if(strlen($hex[$i] = dechex($rgb[$i])) == 1){
            $hex[$i] = "0".$hex[$i];
        }
    }
    return $hex;
}
/* Example */
print_r(rgb2hex(array(10,255,255)));

mina86 at tlen dot pl (05-Feb-2004 05:05)

Easiest :P way to create random hex color:

<?php
function rand_color() {
    return substr('00000' . dechex(mt_rand(0, 0xffffff)), -6);
}
?>

paeppi at actionorg dot de (30-Dec-2003 06:53)

Easier way to create random hex color:

<?php

function rand_color() {
    $hexcolor = dechex(mt_rand(0,16777215));

    while (strlen($hexcolor) < 6) {
        $hexcolor = $hexcolor."0";
    }
    return $hexcolor;
}

echo "#".rand_color();
?>

huda m elmatsani <justhuda at netscape dot net> (16-Sep-2003 11:36)

Create Random Hex Color:

function make_seed() {
   list($usec, $sec) = explode(' ', microtime());
   return (float) $sec + ((double) $usec * 100000);
}

function rand_hex() {
   mt_srand(make_seed());
   $randval = mt_rand(0,255);
   //convert to hex
   return sprintf("%02X",$randval);
}

function random_color(){
   return "#".rand_hex().rand_hex().rand_hex();
}

hme ;)

paeppi at actionorg dot de (04-Aug-2003 03:42)

# One example how to convert a decimal number into any other system (here 32 digits -- 0 to v) and how to convert back.
# Just replace the "32" in my functions with the number of digits in "your" system, and continue the replace-lists.
# This is surely not the very best way to do this, but it hopefully helps :-)

function decttw($int_dec) {
    $s = $int_dec;
    while ($i < 19) {
        $exp = pow(32,18 - $i);
        $modulo = fmod($s,$exp);
        $value = ($s - $modulo) / $exp;
        if (($value > 0) && ($start != 1)) {
            $start = 1;
        }
        if ($start == 1) {
            $decs = $value;
            $decs = ereg_replace ("10", "a", $decs);
            $decs = ereg_replace ("11", "b", $decs);
            $decs = ereg_replace ("12", "c", $decs);
            $decs = ereg_replace ("13", "d", $decs);
            $decs = ereg_replace ("14", "e", $decs);
            $decs = ereg_replace ("15", "f", $decs);
            $decs = ereg_replace ("16", "g", $decs);
            $decs = ereg_replace ("17", "h", $decs);
            $decs = ereg_replace ("18", "i", $decs);
            $decs = ereg_replace ("19", "j", $decs);
            $decs = ereg_replace ("20", "k", $decs);
            $decs = ereg_replace ("21", "l", $decs);
            $decs = ereg_replace ("22", "m", $decs);
            $decs = ereg_replace ("23", "n", $decs);
            $decs = ereg_replace ("24", "o", $decs);
            $decs = ereg_replace ("25", "p", $decs);
            $decs = ereg_replace ("26", "q", $decs);
            $decs = ereg_replace ("27", "r", $decs);
            $decs = ereg_replace ("28", "s", $decs);
            $decs = ereg_replace ("29", "t", $decs);
            $decs = ereg_replace ("30", "u", $decs);
            $decs = ereg_replace ("31", "v", $decs);
            $int_value = $int_value.$decs;
        }
        $s = $s - $value * $exp;
        $i++;
    }
    return $int_value;
}

function ttwdec($int_ttw) {
    $digits = strlen($int_ttw);
    while ($i < $digits) {
        $s = substr($int_ttw,$i,1);
        $decs = $s;
        $decs = ereg_replace ("a", "10", $decs);
        $decs = ereg_replace ("b", "11", $decs);
        $decs = ereg_replace ("c", "12", $decs);
        $decs = ereg_replace ("d", "13", $decs);
        $decs = ereg_replace ("e", "14", $decs);
        $decs = ereg_replace ("f", "15", $decs);
        $decs = ereg_replace ("g", "16", $decs);
        $decs = ereg_replace ("h", "17", $decs);
        $decs = ereg_replace ("i", "18", $decs);
        $decs = ereg_replace ("j", "19", $decs);
        $decs = ereg_replace ("k", "20", $decs);
        $decs = ereg_replace ("l", "21", $decs);
        $decs = ereg_replace ("m", "22", $decs);
        $decs = ereg_replace ("n", "23", $decs);
        $decs = ereg_replace ("o", "24", $decs);
        $decs = ereg_replace ("p", "25", $decs);
        $decs = ereg_replace ("q", "26", $decs);
        $decs = ereg_replace ("r", "27", $decs);
        $decs = ereg_replace ("s", "28", $decs);
        $decs = ereg_replace ("t", "29", $decs);
        $decs = ereg_replace ("u", "30", $decs);
        $decs = ereg_replace ("v", "31", $decs);
        $i++;
        $value = $decs * pow(32,($digits - $i));
        $int_value = $int_value + $value;
    }
    return $int_value;
}

m0sh3 at hotmail dot com (30-Jul-2003 01:41)

This will can convert decimal of more than 2^48 in any PHP version:

$hex = dechex($dec>>24).dechex($dec & 0xFFFFFF)

allan-wegan at allan-wegan dot de (19-Jul-2003 06:53)

now, here is a nice and small function to convert integers to hex strings and it avoids use of the DECHEX funtion because that function changed it's behavior too often in the past (now, in PHP version 4.3.2 it works with numbers bigger than 0x7FFFFFFF correctly, but i need to be backward compatible).

function &formatIntegerForOutput($value) {
    $text = "00000000";
    $transString = "0123456789ABCDEF";
    // handle highest nibble (nibble 7):
        $nibble = $value & 0x70000000;
        $nibble >>= 28;
        if ($value < 0) {
            $nibble = $nibble | 0x00000008;
        }
        $text[0] = $transString[$nibble];
        $value &= 0x0FFFFFFF;
    // nibbles 0 to 6:
        for ($a = 7; $a > 0; $a --) {
            $nibble = $value & 0x0000000F;
            $text[$a] = $transString[$nibble];
            $value >>= 4;
        }
    return $text
}

this function should be not too slow and is really simple.
I don't know, if the DECHEX function in the future will pad it's output to ever be 8 characters in length - so for backward compatibility reasons even in future PHP versions i avoided to use it.

paoligno at tin dot it (15-Mar-2003 03:32)

you can use this workaround (raw but simple and efficient)

$string=DecHex($string*1)

bye bye

the_tenth at pandora dot be (29-Sep-2002 10:12)

<?

function dec2hex($number) {
$length=16;
$hexval="";
while ($number>0) {
$remainder=bcmod($number,16);
if ($remainder<10)
$hexval=$remainder.$hexval;
elseif ($remainder==10)
$hexval="A".$hexval;
elseif ($remainder==11)
$hexval="B".$hexval;
elseif ($remainder==12)
$hexval="C".$hexval;
elseif ($remainder==13)
$hexval="D".$hexval;
elseif ($remainder==14)
$hexval="E".$hexval;
elseif ($remainder==15)
$hexval="F".$hexval;
$number=bcdiv($number,16);
}
while (strlen($hexval)<$length) $hexval="0".$hexval;
return $hexval;
}

$tmp = "<table width='643' border='1'>";
$x = 1;
$y = 1;
$z = dec2hex($x);
$q = dec2hex($y);
for ($i=1;$i<65;$i++){
    $x= bcpow(2,($i-1));
    $z = dec2hex($x);
    $tmp .="<tr><td width='20' align='center' bgcolor='#808080'><font color='#ffffff'>". $i;
    $tmp .="</font></td><td width='5'>2<sup>". ($i-1) . "</sup></td><td width='2'>=</td></td><td>" . $x . "</td>";
    $tmp .="<td>".$z."</td><td>".$y."</td><td>".$q."</td></tr>";
    $y = bcsub(bcpow(2,$i+1),1);
    $q = dec2hex($y);
   
}
$tmp .= "</table>";
echo $tmp;
?>

monkyNOSPAM at phpfi dot org dot invalid (24-Sep-2002 03:20)

Here's how to use bitwise operations for RGB2hex conversion. This function returns hexadesimal rgb value just like one submitted by gurke@bigfoot.com above.

function hexColor($color) {
  return dechex(($color[0]<<16)|($color[1]<<8)|$color[2]);
}

example:

$col[0] = 25;
$col[1] = 255;
$col[2] = 55;

print hexColor($col);

joost at bingopaleis dot com (28-Apr-2002 05:21)

Here are two functions that will convert large dec numbers to hex and vice versa. And I really mean LARGE, much larger than any function posted earlier.

<pre>
// Input: A decimal number as a String.
// Output: The equivalent hexadecimal number as a String.
function dec2hex($number)
{
    $hexvalues = array('0','1','2','3','4','5','6','7',
               '8','9','A','B','C','D','E','F');
    $hexval = '';
     while($number != '0')
     {
        $hexval = $hexvalues[bcmod($number,'16')].$hexval;
        $number = bcdiv($number,'16',0);
    }
    return $hexval;
}

// Input: A hexadecimal number as a String.
// Output: The equivalent decimal number as a String.
function hex2dec($number)
{
    $decvalues = 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');
    $decval = '0';
    $number = strrev($number);
    for($i = 0; $i < strlen($number); $i++)
    {
        $decval = bcadd(bcmul(bcpow('16',$i,0),$decvalues[$number{$i}]), $decval);
    }
    return $decval;
}
</pre>

jfren484 at hotmail dot com (12-Feb-2002 11:47)

Here's a function which works for decimal values up to 9007199254740992 (hex 20000000000000).

function dec2hex($dec)
{
  $hex = ($dec == 0 ? '0' : '');

  while ($dec > 0)
  {
    $hex = dechex($dec - floor($dec / 16) * 16) . $hex;
    $dec = floor($dec / 16);
  }

  return $hex;
}

kristoffer at caveo dot se (11-Feb-2002 01:39)

Heres a example of dec to html hex gradient. Have fun :)

//Amount of gradients
$l = 20;

//Start color
$start[0] = "255";     //red
$start[1] = "0";     //green
$start[2] = "255";     //blue

//End color
$end[0] = "255";     //red
$end[1] = "255";    //green
$end[2] = "255";    //blue

for ($t = 1; $t < $l;) {

    $x = $x * $t;

    for ($i = 0; $i < 3;) {

        $buffer[$i] = $start[$i] - $end[$i];
        $buffer[$i] = floor($buffer[$i] / $l);
        $rgb[$i] = $start[$i] - ($buffer[$i] * $t);

        if ($rgb[$i] > 255) {

            $rgb[$i] = 255;

        }

        $rgb[$i] = dechex($rgb[$i]);
        $rgb[$i] = strtoupper($rgb[$i]);

        if (strlen($rgb[$i]) < 2) {

            $rgb[$i] = "0$rgb[$i]";

        }

        $i++;

    }

    $color = "$rgb[0]$rgb[1]$rgb[2]";
    echo "$color";
        $t++;

}

?>