base_convert
(PHP 4, PHP 5, PHP 7, PHP 8)
base_convert — 数値の基数を任意に変換する
説明
num を基数 to_base
で表した文字列を返します。
num の基数は、
from_base で指定します。
from_base および to_base
は、ともに 2 から 36 までである必要があります。
10 より大きな基数を有する数の各桁は、文字 a-z で表されます。
この場合、a は 10、b は 11、z は 35 を意味します。
num は、大文字小文字を区別せずに扱います。
パラメータ
num-
変換する数値。
numに無効な文字が含まれている場合は、 何もエラーを出さずにただ無視します。 PHP 7.4.0 以降は、無効な文字を与えることは推奨されません。 from_base-
変換前の
numの基数。 to_base-
変換後の
numの基数。
戻り値
num を基数 to_base
で表した値を返します。
変更履歴
| バージョン | 説明 |
|---|---|
| 7.4.0 | 無効な文字を与えると、非推奨の警告が出るようになりました。 結果は不正な文字がなかったかのように計算されます。 |
例
例1 base_convert() の例
<?php
$hexadecimal = 'a37334';
echo base_convert($hexadecimal, 16, 2);
?>上の例の出力は以下となります。
101000110111001100110100
＋add a note
User Contributed Notes 26 notes
PHPCoder at niconet2k dot com ¶
13 years ago
Convert an arbitrarily large number from any base to any base.
string convBase(string $numberInput, string $fromBaseInput, string $toBaseInput)
$numberInput number to convert as a string
$fromBaseInput base of the number to convert as a string
$toBaseInput base the number should be converted to as a string
examples for $fromBaseInput and $toBaseInput
'0123456789ABCDEF' for Hexadecimal (Base16)
'0123456789' for Decimal (Base10)
'01234567' for Octal (Base8)
'01' for Binary (Base2)
You can really put in whatever you want and the first character is the 0.
Examples:
<?php
convBase('123', '0123456789', '01234567');
//Convert '123' from decimal (base10) to octal (base8).
//result: 173
convBase('70B1D707EAC2EDF4C6389F440C7294B51FFF57BB', '0123456789ABCDEF', '01');
//Convert '70B1D707EAC2EDF4C6389F440C7294B51FFF57BB' from hexadecimal (base16) to binary (base2).
//result:
//111000010110001110101110000011111101010110000101110
//110111110100110001100011100010011111010001000000110
//001110010100101001011010100011111111111110101011110
//111011
convBase('1324523453243154324542341524315432113200203012', '012345', '0123456789ABCDEF');
//Convert '1324523453243154324542341524315432113200203012' from senary (base6) to hexadecimal (base16).
//result: 1F9881BAD10454A8C23A838EF00F50
convBase('355927353784509896715106760','0123456789','Christopher');
//Convert '355927353784509896715106760' from decimal (base10) to undecimal (base11) using "Christopher" as the numbers.
//result: iihtspiphoeCrCeshhorsrrtrh
convBase('1C238Ab97132aAC84B72','0123456789aAbBcCdD', '~!@#$%^&*()');
//Convert'1C238Ab97132aAC84B72' from octodecimal (base18) using '0123456789aAbBcCdD' as the numbers to undecimal (base11) using '~!@#$%^&*()' as the numbers.
//result: !%~!!*&!~^!!&(&!~^@#@@@&
function convBase($numberInput, $fromBaseInput, $toBaseInput)
{
if ($fromBaseInput==$toBaseInput) return $numberInput;
$fromBase = str_split($fromBaseInput,1);
$toBase = str_split($toBaseInput,1);
$number = str_split($numberInput,1);
$fromLen=strlen($fromBaseInput);
$toLen=strlen($toBaseInput);
$numberLen=strlen($numberInput);
$retval='';
if ($toBaseInput == '0123456789')
{
$retval=0;
for ($i = 1;$i <= $numberLen; $i++)
$retval = bcadd($retval, bcmul(array_search($number[$i-1], $fromBase),bcpow($fromLen,$numberLen-$i)));
return $retval;
}
if ($fromBaseInput != '0123456789')
$base10=convBase($numberInput, $fromBaseInput, '0123456789');
else
$base10 = $numberInput;
if ($base10<strlen($toBaseInput))
return $toBase[$base10];
while($base10 != '0')
{
$retval = $toBase[bcmod($base10,$toLen)].$retval;
$base10 = bcdiv($base10,$toLen,0);
}
return $retval;
}
?>
ardavies at tiscali dot co dot uk ¶
10 years ago
In order to convert base 26 (hexavigesimal) of just alphanumeric characters (A-Z), wthout integers, (as descibed at http://en.wikipedia.org/wiki/Hexavigesimal), I found this to be useful:
function base_convert_alpha( $str, $from, $to )
{
$r = range( 'A', 'Z' );
$clean = str_replace( $r, array_keys($r), $str );
return base_convert( $clean, $from, $to );
}
echo base_convert_alpha( "BAC", 26, 10 );
//$clean = 102 which then returns 678
Anonymous ¶
6 years ago
While not immediately clear from the description above, a negative sign is also "silently ignored".
base_convert("-12", 10, 10) => 12
Clifford dot ct at gmail dot com ¶
12 years ago
If you use base_convert to convert a large (eg. 80-bit) hexadecimal to base-36, you might observe:
ABCDEF00001234567890 (hexadecimal) => 3O47RE02JZSW0KS8 (base-36) => ABCDEF00001240000000 (hexadecimal)
This is normal and is due to the loss of precision on large numbers.
I have written a string-based function using the built-in BC Math Extension which will overcome this and similar problems.
<?php
function str_baseconvert($str, $frombase=10, $tobase=36) {
$str = trim($str);
if (intval($frombase) != 10) {
$len = strlen($str);
$q = 0;
for ($i=0; $i<$len; $i++) {
$r = base_convert($str[$i], $frombase, 10);
$q = bcadd(bcmul($q, $frombase), $r);
}
}
else $q = $str;
if (intval($tobase) != 10) {
$s = '';
while (bccomp($q, '0', 0) > 0) {
$r = intval(bcmod($q, $tobase));
$s = base_convert($r, 10, $tobase) . $s;
$q = bcdiv($q, $tobase, 0);
}
}
else $s = $q;
return $s;
}
?>
Typical use-cases:
1. Convert a large arbitrary precision number to base-36.
2. Convert a 32-char hexadecimal UUID (128-bit) to a 25-char base-36 unique key, and vice versa.
Examples:
<?php
$b16 = 'ABCDEF00001234567890';
$b36 = str_baseconvert($b16, 16, 36);
echo ("$b16 (hexadecimal) = $b36 (base-36) \\n");
$uuid = 'ABCDEF01234567890123456789ABCDEF';
$ukey = str_baseconvert($uuid, 16, 36);
echo ("$uuid (hexadecimal) = $ukey (base-36) \\n");
?>
ABCDEF00001234567890 (hexadecimal) = 3o47re02jzqisvio (base-36)
ABCDEF01234567890123456789ABCDEF (hexadecimal) = a65xa07491kf5zyfpvbo76g33 (base-36)
JR ¶
13 years ago
Short arabic2roman conveter:
<?php
function rome($N){
$c='IVXLCDM';
for($a=5,$b=$s='';$N;$b++,$a^=7)
for($o=$N%$a,$N=$N/$a^0;$o--;$s=$c[$o>2?$b+$N-($N&=-2)+$o=1:$b].$s);
return $s;
}
?>
And it works :)
lindsay at bitleap dot com ¶
19 years ago
If you need to use base_convert with numbers larger then 32 bit, the following gmp implementation of base_convert should work.
<?php
/*use gmp library to convert base. gmp will convert numbers > 32bit*/
function gmp_convert($num, $base_a, $base_b)
{
return gmp_strval ( gmp_init($num, $base_a), $base_b );
}
?>
Theriault ¶
15 years ago
If you would like to convert numbers into just the uppercase alphabet base and vice-versa (e.g. the column names in a Microsoft Windows Excel sheet..A-Z, AA-ZZ, AAA-ZZZ, ...), the following functions will do this.
<?php
/**
* Converts an integer into the alphabet base (A-Z).
*
* @param int $n This is the number to convert.
* @return string The converted number.
* @author Theriault
*
*/
function num2alpha($n) {
$r = '';
for ($i = 1; $n >= 0 && $i < 10; $i++) {
$r = chr(0x41 + ($n % pow(26, $i) / pow(26, $i - 1))) . $r;
$n -= pow(26, $i);
}
return $r;
}
/**
* Converts an alphabetic string into an integer.
*
* @param int $n This is the number to convert.
* @return string The converted number.
* @author Theriault
*
*/
function alpha2num($a) {
$r = 0;
$l = strlen($a);
for ($i = 0; $i < $l; $i++) {
$r += pow(26, $i) * (ord($a[$l - $i - 1]) - 0x40);
}
return $r - 1;
}
?>
Microsoft Windows Excel stops at IV (255), but this function can handle much larger. However, English words will start to form after a while and some may be offensive, so be careful.
AdamJacobMuller at AdamJacobMuller dot com ¶
20 years ago
<?php
function binarycodedstring2dec($binary) {
$len=strlen($binary);
$rows=($len/4)-1;
if (($len%4)>0) {
$pad=$len+(4-($len%4));
$binary=str_pad($binary,$pad,"0",STR_PAD_LEFT);
$len=strlen($binary);
$rows=($len/4)-1;
}
$x=0;
for ($x=0;$x<=$rows;$x++) {
$s=($x*4);
$bins=$binary[$s].$binary[$s+1].$binary[$s+2].$binary[$s+3];
$num=base_convert($bins,2,10);
if ($num>9) {
die("the string is not a proper binary coded decimal\n");
} else {
$res.=$num;
}
}
return $res;
}
?>
a binary coded decimal is converted by taking groups of four from a decimal string,
for example the binary coded decimal string
1000 = 8
10001000 does not = 136 but 88
so
binarycodedstring2dec(1000) = 8
binarycodedstring2dec(11100000111001)=3839
binarycodedstring2dec(100000111001)=839
i truly have no idea if this function will be useful to anyone, i simply failed a physics midterm because i didn't know this so i wrote this function to make sure i would never forget how to convert binary coded decimals
xdv43 at yandex dot ru ¶
2 years ago
Convert Large Integer to Hexadecimal without PHP Math extension.
<?php
/*
* Created by Michael Renner 17-May-2006 03:24
*/
function baseConvert($numstring, $frombase, $tobase)
{
$chars = "0123456789abcdefghijklmnopqrstuvwxyz";
$tostring = substr($chars, 0, $tobase);
$length = strlen($numstring);
$result = '';
for ($i = 0; $i < $length; $i++)
{
$number[$i] = strpos($chars, $numstring[$i]);
}
do
{
$divide = 0;
$newlen = 0;
for ($i = 0; $i < $length; $i++)
{
$divide = $divide * $frombase + $number[$i];
if ($divide >= $tobase)
{
$number[$newlen++] = (int)($divide / $tobase);
$divide = $divide % $tobase;
} elseif ($newlen > 0)
{
$number[$newlen++] = 0;
}
}
$length = $newlen;
$result = $tostring[$divide] . $result;
} while ($newlen != 0);
return $result;
}
tika dot pahadi at selu dot edu ¶
8 years ago
Note that the method can only convert max 1024 long numbers. Most people don't nee that but once I ran into an issue where binary string was converted into alphanumeric. In such case, you need to split them, convert them and join.
cyrilbele at yahoo dot fr ¶
15 years ago
If you want to do sharding, at some point you will need to decide which shard to target. Here is a simple function to assign the data to a particular shard based on a key (usually identifier of the row)
Here is a simple function to get the shard based on the key and the number of shards available
<?php
function getShard($key,$nbShards) {
$num = substr(base_convert(sha1($key), 16, 10),4,6);
return $num%$nbShards;
}
?>
wadelau at gmail dot com ¶
6 years ago
Base62x gives an alternative way for traditional Base62 and/or Base64.
base62x_encode / base62x_decode would be merged into PHP as an extra module in the future.
Prior to that, users can download the PHP extra module via: https://github.com/wadelau/Base62x
ohcc at 163 dot com ¶
7 years ago
<?php
$v = base_convert(3.14, 10, 10);
var_dump($v);
?>
output: string(3) "314"
simon at simonster dot com ¶
20 years ago
Here are some functions for converting integers to and from base 256. Converting to base 64 is simple given these.
<?php
function to_base256($number, $from_base = 10) {
$binary_number = base_convert($number, $from_base, 2);
$final_string = "";
$new_length = (ceil(strlen($binary_number)/8)*8);
$binary_number = str_pad($binary_number, $new_length, "0", STR_PAD_LEFT);
for($i=($new_length-8); $i>=0; $i-=8) {
$final_string = chr(base_convert(substr($binary_number, $i, 8), 2, 10)).$final_string;
}
return $final_string;
}
function from_base256($string, $to_base = 10) {
$number = "";
for($i=0; $i<strlen($string); $i++) {
$number .= str_pad(base_convert(ord($string{$i}), 10, 2), 8, "0", STR_PAD_LEFT);
}
return base_convert($number, 2, $to_base);
}
?>
Yes, I know that this would be more efficient if it used mod instead of base_convert, but it needs to work with integers > 32 bits.
denik dot od at gmail dot com ¶
11 years ago
Convert any length bits to HEX:
function bits2hex($bin)
{
$out = "";
for($i=0;$i<strlen($bin);$i+=8)
{
$byte = substr($bin,$i,8); if( strlen($byte)<8 ) $byte .= str_repeat('0',8-strlen($byte));
$out .= base_convert($byte,2,16);
}
return $out;
}
VARNING! If the last byte is incomplete, it is supplemented with zeros as string!
Anonymous ¶
6 years ago
some other mini implementation of base32 without error catching. just bring things from 5 to 8 and 8 to 5 bit. greetings. mho
<?
function base32_decode($d)
{
list($t, $b, $r) = array("ABCDEFGHIJKLMNOPQRSTUVWXYZ234567", "", "");
foreach(str_split($d) as $c)
$b = $b . sprintf("%05b", strpos($t, $c));
foreach(str_split($b, 8) as $c)
$r = $r . chr(bindec($c));
return($r);
}
function base32_encode($d)
{
list($t, $b, $r) = array("ABCDEFGHIJKLMNOPQRSTUVWXYZ234567", "", "");
foreach(str_split($d) as $c)
$b = $b . sprintf("%08b", ord($c));
foreach(str_split($b, 5) as $c)
$r = $r . $t[bindec($c)];
return($r);
}
?>
fiftytoo at buckeyeexpress dot com ¶
20 years ago
I needed a function to invert a hex value, which i used for setting font colors when they were on a colored background, that way i will get a contrasting color.
Im sure there are other reasons to use this, you decide!!
<?php
function InvertColor($hex) {
return sprintf("%06s",base_convert(($hex ^ 0xFFFFFF),10,16));
};
print '<td bgcolor="BB2222"><font color="'.InvertColor(0xBB2222).'">Blah</font></td>';
// Prints 44dddd as the font color, which is it's opposite on the color wheel
?>