dechex
(PHP 4, PHP 5, PHP 7, PHP 8)
dechex — 十进制转换为十六进制
说明
返回一字符串，包含有给定
num
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。
返回值
num 的16进制表示
示例
示例 #1 dechex() 示例
<?php
echo dechex(10) . "\n";
echo dechex(47);
?>以上示例会输出：
a 2f
示例 #2 大整数的 dechex() 示例
<?php
// 下面的输出假设是 32 位平台。
// 注意输出的所有值一样。
echo dechex(-1)."\n";
echo dechex(PHP_INT_MAX * 2 + 1)."\n";
echo dechex(pow(2, 32) - 1)."\n";
?>以上示例会输出：
ffffffff ffffffff ffffffff
＋添加备注
用户贡献的备注 17 notes
brent ¶
18 years ago
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.
joost at bingopaleis dot com ¶
22 years ago
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 $decval;
}
</pre>
jrisken at mn dot rr dot com ¶
19 years ago
A less elegant but (perhaps) faster way to pad is with substr with a negative length argument. I use it in this tiny function which formats computed rgb color codes for style sheets:
<?
function toColor($n)
{
return("#".substr("000000".dechex($n),-6));
}
?>
mina86 at tlen dot pl ¶
21 years ago
Easiest :P way to create random hex color:
<?php
function rand_color() {
return substr('00000' . dechex(mt_rand(0, 0xffffff)), -6);
}
?>
Anonymous ¶
20 years ago
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));
}
$hex = random_hex_color(); // 09B826
?>
Enjoy.
baoquyen804 at gmail dot com ¶
10 years ago
this base function convert string rgb to color
<?php
function rgb_to_color($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
?>
sneskid at hotmail dot com ¶
12 years ago
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' . $str + 0) is faster than hexdec()
Mista-NiceGuy at web dot de ¶
19 years ago
These are functions to convert roman numbers (e.g. MXC) into dec and vice versa.
Note: romdec() does not check whether a string is really roman or not. To force a user-input into a real roman number use decrom(romdec($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 $retval;
}
echo decrom(romdec("XXXX"));
?>
admin AT bobfrank DOT org ¶
19 years ago
Here is a very small zeropadding that you can use for numbers:
function zeropad($num, $lim)
{
return (strlen($num) >= $lim) ? $num : zeropad("0" . $num);
}
zeropad("234",6);
will produce:
000234
zeropad("234",1);
will produce:
234
monkyNOSPAM at phpfi dot org dot invalid ¶
22 years ago
Here's how to use bitwise operations for RGB2hex conversion. This function returns hexadesimal rgb value just like one submitted by gurke@bigfoot.com above.
function hexColor($color) {
return dechex(($color[0]<<16)|($color[1]<<8)|$color[2]);
}
example:
$col[0] = 25;
$col[1] = 255;
$col[2] = 55;
print hexColor($col);
jbleau at gmail dot com ¶
16 years ago
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 . $h;
}
?>
delchodimi at gmail dot com ¶
9 years ago
I like the example with the bitwise operations but if the value of color[0] is less than 16 it's not accurate:
example:
color[0]: 0;
color[1]: 0;
color[2]: 255;
function hexColor($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".$rgb, -6));
}
------------------------------------------------------
huda m elmatsani <justhuda at netscape dot net> ¶
21 years ago
Create Random Hex Color:
function make_seed() {
list($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 ;)
andries at centim dot be ¶
12 years ago
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
mountarreat at gmail dot com ¶
16 years ago
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);
}
?>