Diese Seite bei php.net
The PHP manual text and comments are covered by the Creative Commons Attribution 3.0 License © the PHP Documentation Group - Impressum - mail("TO:Reinhard Neidl",...)
(PHP 4, PHP 5)
dechex — Dezimal zu Hexadezimal Umwandlung
Konvertiert einen Wert number in eine hexadezimale Stringdarstellung. Der größte konvertierbare Wert ist 4294967295 (dezimal) bwz. "ffffffff" (hexadezimal).
Der umzuwandelnde Wert
Die hexadezimale Stringdarstellung von number
Beispiel #1 dechex() Beispiel
<?php
echo dechex(10) . "\n";
echo dechex(47);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
a 2f
<?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 $return."\n";
?>
I was confused by dechex's size limitation. Here is my solution to the problem. It supports much bigger values, as well as signs.
<?php
function dec_to_hex($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 . $h;
}
?>
I was challenged by a problem with large number calculations and conversion to hex within php. The calculation exceeded unsigned integer and even float range. You can easily change it for your needs but it is, thanks to bcmath, capable of handling big numbers via string. This function will convert them to hex.
In this specific example though, since I use it for game internals that can only handle 32 bit numbers, it will truncate calculations at 8 digits. If the input is 1 for example it will be filled up with zeros. Output 00000001h.
Of course I don't claim it to be a good one, but it works for me and my purpose. Suggestions on faster code welcome!
<?php
// Turns numbers into 32-bit hex string; Fills up zeros
function lrgDec2Hex($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);
}
?>
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'
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.
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, $i, 1) ) ) ;
}
?>
These are functions to convert roman numbers (e.g. MXC) into dec and vice versa.
Note: romdec() does not check whether a string is really roman or not. To force a user-input into a real roman number use decrom(romdec($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"));
?>
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 $out;
}
?>
Example: color_mkwebsafe('0e5c94');
Produces: 006699
Hope this helps someone out... Happy coding. :-)
simple, non-recursive way of zerofilling (why making everything complicated, there r more than enough inbuilt functions)
function zfill($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! :)
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 $lim
}
?>
Warning for use on 64 bit machines! The Extra length matters!
32bit machine:
php -r 'echo dechex(4294967295);'
output: ffffffff
64bit machine:
php -r 'echo dechex(4294967295);'
output: ffffffff
so far it is ok. But for slightly bigger numbers:
32bit machine:
php -r 'echo dechex(4294967296);'
output: 0
64bit machine:
php -r 'echo dechex(4294967296);'
output: 100000000
note the difference!
This is particularly important when converting negative numbers:
64bit machine:
php -r 'echo dechex(-1);'
output: ffffffffffffffff
32bit machine:
php -r 'echo dechex(-1);'
output: ffffffff
If you want your code to be portable to amd64 or xeons (which are now quite popular with hosting companies) then you must ensure that your code copes with the different length of the result for negative numbers (and the max value, although that is probably less critical).
A less elegant but (perhaps) faster way to pad is with substr with a negative length argument. I use it in this tiny function which formats computed rgb color codes for style sheets:
<?
function toColor($n)
{
return("#".substr("000000".dechex($n),-6));
}
?>
Here is a very small zeropadding that you can use for numbers:
function zeropad($num, $lim)
{
return (strlen($num) >= $lim) ? $num : zeropad("0" . $num);
}
zeropad("234",6);
will produce:
000234
zeropad("234",1);
will produce:
234
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;
}
}
}
?>
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, $color2 the end color.
I hope this helps somebody.
I see a lot of less-than-optimal functions posted on this page, so I feel I have to give some better examples...
due to the sheer size of this collection, I have made it available on my server, rather than copy/paste it into these comments.
http://ryo-ohki.4th-age.com/demos/able.php
and
http://ryo-ohki.4th-age.com/demos/able.phps
dechex replacement function from above source:
<?php
define('BIT_BYTE', 8); // bits per byte
define('HEX_BYTE', BIT_BYTE/4); // hex digits in a byte
define('BIT_INT', 32); // sizeof(int)
define('HEX_INT', BIT_INT / (BIT_BYTE/HEX_BYTE)); // hex digits in an int
function i2h($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 $ret;
}
echo i2h(rand(1,2)==1?-mt_rand():mt_rand());
?>
This function will take a string and convert it into a hexdump.
e.g.
3c666f6e 74207369 7a653d22 33223e4c <font.size."3">L
6561726e 20686f77 20746f20 62652061 earn.how.to.be.a
function hexdump($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;
}
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));
}
$hex = random_hex_color(); // 09B826
?>
Enjoy.
If you need to convert RGB-color into HEX-color, use this:
<?php
function rgb2hex($rgb){
return sprintf("%06X", $rgb);
}
$hex = rgb2hex(65280); // 00FF00
?>
this function generates an hex-colorcode out of a string.
usefull if you want to show a list of words all in different colors, that should remain its color even if the order changes.
(if the string is empty, it gives back a random color)
function word2color($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 $r;
}
<?php
/*
here are two functions, some might find them useful (maybe for encoding)
converting string to hex and hex to string:
*/
function strhex($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 $string;
}
?>
Here's my version of a red->yellow->green gradient:
<?php
function colorMeter($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>".$RGB."</PRE></TD></TR>\n";
}
?>
</TABLE>
/*
* RGB-Colorcodes(i.e: 255 0 255) to HEX-Colorcodes (i.e: FF00FF)
*/
function rgb2hex($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)));
Easiest :P way to create random hex color:
<?php
function rand_color() {
return substr('00000' . dechex(mt_rand(0, 0xffffff)), -6);
}
?>
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 $hexcolor;
}
echo "#".rand_color();
?>
Create Random Hex Color:
function make_seed() {
list($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 ;)
# 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;
}
This will can convert decimal of more than 2^48 in any PHP version:
$hex = dechex($dec>>24).dechex($dec & 0xFFFFFF)
now, here is a nice and small function to convert integers to hex strings and it avoids use of the DECHEX funtion because that function changed it's behavior too often in the past (now, in PHP version 4.3.2 it works with numbers bigger than 0x7FFFFFFF correctly, but i need to be backward compatible).
function &formatIntegerForOutput($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.
you can use this workaround (raw but simple and efficient)
$string=DecHex($string*1)
bye bye
<?
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 $tmp;
?>
Here's how to use bitwise operations for RGB2hex conversion. This function returns hexadesimal rgb value just like one submitted by gurke@bigfoot.com above.
function hexColor($color) {
return dechex(($color[0]<<16)|($color[1]<<8)|$color[2]);
}
example:
$col[0] = 25;
$col[1] = 255;
$col[2] = 55;
print hexColor($col);
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 $decval;
}
</pre>
Here's a function which works for decimal values up to 9007199254740992 (hex 20000000000000).
function dec2hex($dec)
{
$hex = ($dec == 0 ? '0' : '');
while ($dec > 0)
{
$hex = dechex($dec - floor($dec / 16) * 16) . $hex;
$dec = floor($dec / 16);
}
return $hex;
}
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++;
}
?>
Diese Seite bei php.net