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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 PHP_INT_MAX * 2 + 1 (或 -1)：在 32 位平台上是十进制的 4294967295，其 dechex() 的结果为 ffffffff。

参数

number

要转换的十进制值

PHP 的 integer 类型是有符号的，但 dechex() 处理无符号整数，负正数会以无符号处理。

返回值

number 的16进制表示

范例

Example #1 dechex() 例子

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

以上例程会输出：

a
2f

Example #2 大整数的 dechex() 例子

  <?php
 // The output below assumes a 32-bit platform.
// Note that the output is the same for all values.
 echo  dechex (- 1 ). "\n" ;
echo  dechex ( PHP_INT_MAX  *  2  +  1 ). "\n" ;
echo  dechex ( pow ( 2 ,  32 ) -  1 ). "\n" ;
 ?>

以上例程会输出：

ffffffff
ffffffff
ffffffff

参见

hexdec() - 十六进制转换为十进制
decbin() - 十进制转换为二进制
decoct() - 十进制转换为八进制
base_convert() - 在任意进制之间转换数字

用户评论:

[#1] delchodimi at gmail dot com [2015-04-30 14:43:58]

I like the example with the bitwise operations but if the value of color[0] is less than 16 it's not accurate:
example:
color[0]: 0;
color[1]: 0;
color[2]: 255;
function hexColor($color) {
  return dechex(($color[0]<<16)|($color[1]<<8)|$color[2]);
}
It returns "ff", which is not legit RGB color...
so my solution is to combine the function above with:
function toColor($n)
{
return("#".substr("000000".dechex($n),-6));
}

If you gotta deal with array of rgb values this is my solution:
------------------------------------------------------
function hexColor($color) {
    $rgb = dechex(($color[0]<<16)|($color[1]<<8)|$color[2]);
    return("#".substr("000000".$rgb, -6));
}
------------------------------------------------------

[#2] baoquyen804 at gmail dot com [2014-09-01 21:16:55]

this base function convert string rgb to color
<?php function rgb_to_color($rgb, $symbols=' '){ $color = ''; $arr = explode($symbols, $rgb); $count = count($arr); for($i=0; $i<$count; $i++){ $color .= dechex($arr[$i]); } return '#'.$color; } echo rgb_to_color('186 186 18'); // #baba12 echo rgb_to_color('186-186-18', '-'); // #baba12 ?>

[#3] jenny-schubert87 dot 1 at web dot de [2014-07-31 22:02:21]

I figured out another way to do this:
if you have a very long decimal number in gmp format (you can always create a gmp number with gmp_init($numberstring), you can simply do gmp_strval($gmpnumber, 16), where $gmpnumber is your gmp number, and the 16 is the base you want to transform it to. Worked for me like a charm, also works for other bases.

[#4] Kory P. [2013-11-10 15:56:25]

Or you could use this for an RGBA color.
    function toAlphaColor($n,$a)
    {
        $rgb = substr("000000".dechex($n),-6);
        $alpha = substr("00".dechex($a),-2);
        return("#".$rgb.$alpha);
    }

[#5] mailderemi at gmail dot com [2012-12-13 14:26:31]

Javascript Crypt:

<?php function jsCrypt($script,$level=1){ for ($j=0;$j<$level;$j++){ $asc=''; for ($i=0;$i<strlen($script);$i++) $asc.='%'.dechex(ord($script[$i])); $script='<SCRIPT LANGUAGE="JavaScript">document.write(unescape(\''.$asc.'\'));</SCRIPT>'; } return $script; } echo jsCrypt('<script>alert(123);</script>',1); ?>

[#6] hmlinks at gmail dot com [2012-10-03 01:02:34]

I wrote this to convert hex into signed int, hope this helps someone out there... peace :)

<?php $hex = dechex(-32767); $dec = shexdex($hex); function shexdex($hex){ $dec = hexdec($hex); // Negative number (in binary if the msb is 1 then it is neg) // since one hex is 4bits, the value 8 and up contain msb of 1, hence negative number if ($hex[0] >= '8'){ // Note: if you use the digit 8 it is not the same as '8' $dec -= 1; $dec = ~$dec; return -$dec; } return $dec; } if ($dec == -32767){ echo 'Yay!'; } ?>

[#7] sneskid at hotmail dot com [2012-03-23 07:09:50]

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()

[#8] andries at centim dot be [2012-03-07 14:44:11]

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

[#9] 9381904 at gmail dot com [2011-11-01 22:11:09]

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 ?>

[#10] jbleau at gmail dot com [2008-10-29 02:23:59]

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; } ?>

[#11] mountarreat at gmail dot com [2008-05-11 09:55:55]

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); } ?>

[#12] sjaak at spoilerfreaks dot com [2007-03-09 07:28:19]

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'

[#13] brent [2006-12-15 23:33:16]

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.

[#14] Mista-NiceGuy at web dot de [2005-12-28 05:00:10]

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")); ?>

[#15] cory at lavacube dot com [2005-10-27 16:45:08]

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. :-)

[#16] oliver at realtsp dot com [2005-06-14 01:46:24]

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).

[#17] jrisken at mn dot rr dot com [2005-05-28 19:33:06]

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:
<?php function toColor($n) { return("#".substr("000000".dechex($n),-6)); } ?>

[#18] admin AT bobfrank DOT org [2005-05-01 19:28:19]

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

[#19] morten at nilsen dot com [2005-01-02 04:30:46]

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()); ?>

[#20] wangster at darkcore dot net [2004-12-14 23:36:00]

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;
}

[#21] [2004-12-12 07:31:31]

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.

[#22] [2004-12-11 13:30:17]

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

[#23] admin[TAKETHISOUT] at torsoft dot no-ip dot com [2004-04-21 12:01:18]

<?php 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; } ?>

[#24] daevid at daevid dot com [2004-03-18 14:59:51]

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>

[#25] thr at recide dot net [2004-02-09 16:39:07]

[#26] mina86 at tlen dot pl [2004-02-05 09:05:38]

Easiest :P way to create random hex color:

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

[#27] huda m elmatsani <justhuda at netscape dot net> [2003-09-16 15:36:00]

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 ;)

[#28] allan-wegan at allan-wegan dot de [2003-07-19 10:53:32]

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.

[#29] monkyNOSPAM at phpfi dot org dot invalid [2002-09-23 19:20:38]

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);

[#30] joost at bingopaleis dot com [2002-04-28 09:21:06]

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>

[#31] jfren484 at hotmail dot com [2002-02-12 15:47:11]

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;
}

[#32] kristoffer at caveo dot se [2002-02-11 05:39:03]

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++;

}

?>