base_convert

(PHP 4, PHP 5, PHP 7, PHP 8)

base_convert在任意进制之间转换数字

说明

base_convert ( string $number , int $frombase , int $tobase ) : string

返回一字符串,包含 numbertobase 进制的表示。number 本身的进制由 frombase 指定。frombasetobase 都只能在 2 和 36 之间(包括 2 和 36)。高于十进制的数字用字母 a-z 表示,例如 a 表示 10,b 表示 11 以及 z 表示 35。

Warning

由于使用内部的 "double" 或 "float" 类型,base_convert() 的操作可能会导致大数值中的精度丢失。请参见本手册的 浮点数 章节以便获得更多详细信息。

参数

number

要转换的数字

frombase

The base number is in

tobase

The base to convert number to

返回值

number converted to base tobase

范例

Example #1 base_convert() 例子

<?php
$hexadecimal 
'A37334';
echo 
base_convert($hexadecimal162);
?>

以上例程会输出:

101000110111001100110100

参见

User Contributed Notes

Anonymous 19-Oct-2018 01:09
While not immediately clear from the description above, a negative sign is also "silently ignored".

base_convert("-12", 10, 10)   =>   12
Anonymous 03-Jan-2018 04:42
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);
    }
?>
wadelau at gmail dot com 28-Dec-2017 09:37
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 29-Aug-2017 06:31
<?php
    $v
= base_convert(3.14, 10, 10);
   
var_dump($v);
?>

output: string(3) "314"
tika dot pahadi at selu dot edu 17-Jan-2016 09:23
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.
liams dot test dot acc at gmail dot com 16-Aug-2015 10:49
I wrote this as part of a college assignment to shorten urls. It works for any base and with any range of characters, eg. A-Za-z0-9 etc. Hope it helps someone.

<?php

        $base
= range(0, 1);
       
$number = 255;

        function
translate($base, $number){

               
$array = array();
               
$n = count($base);
               
$i = $number;

                while(
true){

               
/* by dividing $i % $n we can get the remainder after the number has
                 * been divided by the base. Subtracting the result from $i (number), and dividing
                 * by $n (base) we reassign the result to $i, thus moving on to the next smallest
                 * exponent, and around for another go of the loop. It continues doing this, churning
                 * out the remainders until $i <= 0 at which point it breaks.
                 */
                       
                       
if($i <= 0){

                                break;
                        }else{
                               
$r = ($i % $n);

                             
//reassign the value of $i
                               
$i = ($i - $r) / $n;

                               
$array[] = $base[$r];
                        }
                }
               
$string = implode("", $array);
                return
$string;
        }

       
$string = translate($base, $number);
        echo
$string;
       
       
// prints 11111111
?
ardavies at tiscali dot co dot uk 24-May-2014 11:31
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
andrew at youritland dot co dot uk 29-Apr-2014 03:49
Example of using base_convert to generate random passwords

function random_password()
{
  $rvalue1 = mt_rand(100,999);
  $rvalue2 = time();
  $rvalue3 = mt_rand(1000,9999);
  $rvalue4 = mt_rand(1,9);
  $rvalue5 = mt_rand(101,109);
  //combine values
  $rvalues = intval(((($rvalue2.$rvalue3) + $rvalue1)*$rvalue4) / $rvalue5);
 
  //return value in base-35 (will contain chars from '0' to 'z')
  return base_convert($rvalues,10,35);
}

Change the range of rvalue5 to get more or less characters. This setting
will return 8 chars.
denik dot od at gmail dot com 07-Jun-2013 02:55
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!
Clifford dot ct at gmail dot com 07-Aug-2012 02:01
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)
Baji dot Panchumarti at gmail dot com 04-Jul-2012 07:50
Extending base_convert to bases above 36, up to base 62.

<?php
function base_convert_x( $_number='', $_frBase=10, $_toBase=62 ) {

#   Today's Date - C74 - convert a string (+ve integer) from any arbitrary base to any arbitrary base, up to base 62, using  0-9,A-Z,a-z
#
#   Usage :   echo base_convert_x( 123456789012345, 10, 32 );

 
$_10to62 =  array(
   
'0'  => '0', '1'  => '1', '2'  => '2', '3'  => '3', '4'  => '4', '5'  => '5', '6'  => '6', '7'  => '7', '8'  => '8', '9'  => '9', '00' => '0', '01' => '1', '02' => '2', '03' => '3', '04' => '4', '05' => '5', '06' => '6', '07' => '7',
   
'10' => 'A', '11' => 'B', '12' => 'C', '13' => 'D', '14' => 'E', '15' => 'F', '16' => 'G', '17' => 'H', '18' => 'I', '19' => 'J', '20' => 'K', '21' => 'L', '22' => 'M', '23' => 'N', '24' => 'O', '25' => 'P', '26' => 'Q', '27' => 'R',
   
'30' => 'U', '31' => 'V', '32' => 'W', '33' => 'X', '34' => 'Y', '35' => 'Z', '36' => 'a', '37' => 'b', '38' => 'c', '39' => 'd', '40' => 'e', '41' => 'f', '42' => 'g', '43' => 'h', '44' => 'i', '45' => 'j', '46' => 'k', '47' => 'l',
   
'50' => 'o', '51' => 'p', '52' => 'q', '53' => 'r', '54' => 's', '55' => 't', '56' => 'u', '57' => 'v', '58' => 'w', '59' => 'x', '60' => 'y', '61' => 'z'  );

 
$_62to10 =  array(
   
'0' => '00', '1' => '01', '2' => '02', '3' => '03', '4' => '04', '5' => '05', '6' => '06', '7' => '07', '8' => '08', '9' => '09', 'A' => '10', 'B' => '11', 'C' => '12', 'D' => '13', 'E' => '14', 'F' => '15', 'G' => '16', 'H' => '17',
   
'K' => '20', 'L' => '21', 'M' => '22', 'N' => '23', 'O' => '24', 'P' => '25', 'Q' => '26', 'R' => '27', 'S' => '28', 'T' => '29', 'U' => '30', 'V' => '31', 'W' => '32', 'X' => '33', 'Y' => '34', 'Z' => '35', 'a' => '36', 'b' => '37',
   
'e' => '40', 'f' => '41', 'g' => '42', 'h' => '43', 'i' => '44', 'j' => '45', 'k' => '46', 'l' => '47', 'm' => '48', 'n' => '49', 'o' => '50', 'p' => '51', 'q' => '52', 'r' => '53', 's' => '54', 't' => '55', 'u' => '56', 'v' => '57',
   
'y' => '60', 'z' => '61' );

#   ---- First convert from frBase to base-10

   
$_in_b10        =   0;
   
$_pwr_of_frB    =   1;                        #  power of from base, eg. 1, 8, 64, 512
   
$_chars         =   str_split( $_number );    #  split input # into chars
   
$_str_len       =   strlen( $_number );
   
$_pos           =   0;

    while     ( 
$_pos++ < $_str_len )  {
       
$_char          =   $_chars[$_str_len - $_pos];
       
$_in_b10       +=   (((int) $_62to10[$_char] ) * $_pwr_of_frB);
       
$_pwr_of_frB   *=   $_frBase;
    }

#   ---- Now convert from base-10 to toBase

   
$_dividend      =   (int)   $_in_b10;         #  name dividend easier to follow below
   
$_in_toB        =   '';                       #  number string in toBase

   
while     ( $_dividend > 0 )        {

       
$_quotient  =   (int) ( $_dividend / $_toBase );    #  eg. 789 / 62  =  12  ( C in base 62 )
       
$_remainder =   ''  .  ( $_dividend % $_toBase );   #  789 % 62  =  45  ( j in base 62 )
       
$_in_toB    =   $_10to62[$_remainder] . $_in_toB;   #  789  (in base 10)  =    Cj  (in base 62)
       
$_dividend  =   $_quotient;                         #  new dividend is the quotient from base division
   
}

    if  (
$_in_toB  ==  '' )
         
$_in_toB  =   '0';

    return   
$_in_toB;                           #  base $_toBase string
}
#   --------- examples -------
   
echo base_convert_x( '3456789ABCDEF', 16, 10 ) . "\n";    #  920735923817967
   
echo   base_convert( '3456789ABCDEF', 16, 10 ) . "\n";    #  920735923817967
?>
PHPCoder at niconet2k dot com 17-Nov-2011 10:45
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;
}
?>
bpds 30-Sep-2011 05:47
A simple function to convert an int to any base.

<?php
function intToAlphaBaseN($n,$baseArray) {
   
$l=count($baseArray);
   
$s = '';
    for (
$i = 1; $n >= 0 && $i < 10; $i++) {
       
$s $baseArray[($n % pow($l, $i) / pow($l, $i - 1))].$s;
       
$n -= pow($l, $i);
    }
    return
$s;
}

$alpha=array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z');
$r=rand(0, 99999999999);
echo(
intToAlphaBaseN($r,$alpha));
?>
JR 16-Aug-2011 04:19
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 :)
bryan at bryanruiz dot com 03-Feb-2011 03:11
A RFC 4648 Compliant Base32 encode.  Send me an email if you end up making this thing more efficient with bitwise operations and whatever else.

<?php

/**
 * Encode in Base32 based on RFC 4648.
 * Requires 20% more space than base64 
 * Great for case-insensitive filesystems like Windows and URL's  (except for = char which can be excluded using the pad option for urls)
 *
 * @package default
 * @author Bryan Ruiz
 **/
class Base32 {

   private static
$map = array(
       
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', //  7
       
'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 15
       
'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 23
       
'Y', 'Z', '2', '3', '4', '5', '6', '7', // 31
       
'='  // padding char
   
);
   
   private static
$flippedMap = array(
       
'A'=>'0', 'B'=>'1', 'C'=>'2', 'D'=>'3', 'E'=>'4', 'F'=>'5', 'G'=>'6', 'H'=>'7',
       
'I'=>'8', 'J'=>'9', 'K'=>'10', 'L'=>'11', 'M'=>'12', 'N'=>'13', 'O'=>'14', 'P'=>'15',
       
'Q'=>'16', 'R'=>'17', 'S'=>'18', 'T'=>'19', 'U'=>'20', 'V'=>'21', 'W'=>'22', 'X'=>'23',
       
'Y'=>'24', 'Z'=>'25', '2'=>'26', '3'=>'27', '4'=>'28', '5'=>'29', '6'=>'30', '7'=>'31'
   
);
   
   
/**
     *    Use padding false when encoding for urls
     *
     * @return base32 encoded string
     * @author Bryan Ruiz
     **/
   
public static function encode($input, $padding = true) {
        if(empty(
$input)) return "";
       
$input = str_split($input);
       
$binaryString = "";
        for(
$i = 0; $i < count($input); $i++) {
           
$binaryString .= str_pad(base_convert(ord($input[$i]), 10, 2), 8, '0', STR_PAD_LEFT);
        }
       
$fiveBitBinaryArray = str_split($binaryString, 5);
       
$base32 = "";
       
$i=0;
        while(
$i < count($fiveBitBinaryArray)) {   
           
$base32 .= self::$map[base_convert(str_pad($fiveBitBinaryArray[$i], 5,'0'), 2, 10)];
           
$i++;
        }
        if(
$padding && ($x = strlen($binaryString) % 40) != 0) {
            if(
$x == 8) $base32 .= str_repeat(self::$map[32], 6);
            else if(
$x == 16) $base32 .= str_repeat(self::$map[32], 4);
            else if(
$x == 24) $base32 .= str_repeat(self::$map[32], 3);
            else if(
$x == 32) $base32 .= self::$map[32];
        }
        return
$base32;
    }
   
    public static function
decode($input) {
        if(empty(
$input)) return;
       
$paddingCharCount = substr_count($input, self::$map[32]);
       
$allowedValues = array(6,4,3,1,0);
        if(!
in_array($paddingCharCount, $allowedValues)) return false;
        for(
$i=0; $i<4; $i++){
            if(
$paddingCharCount == $allowedValues[$i] &&
               
substr($input, -($allowedValues[$i])) != str_repeat(self::$map[32], $allowedValues[$i])) return false;
        }
       
$input = str_replace('=','', $input);
       
$input = str_split($input);
       
$binaryString = "";
        for(
$i=0; $i < count($input); $i = $i+8) {
           
$x = "";
            if(!
in_array($input[$i], self::$map)) return false;
            for(
$j=0; $j < 8; $j++) {
               
$x .= str_pad(base_convert(@self::$flippedMap[@$input[$i + $j]], 10, 2), 5, '0', STR_PAD_LEFT);
            }
           
$eightBits = str_split($x, 8);
            for(
$z = 0; $z < count($eightBits); $z++) {
               
$binaryString .= ( ($y = chr(base_convert($eightBits[$z], 2, 10))) || ord($y) == 48 ) ? $y:"";
            }
        }
        return
$binaryString;
    }
}
francesco[at]paladinux.net 23-Sep-2010 03:30
base convert is limited on standard base invented.
In some case, if you want to invented some translate code (for authorizion code 4 example) , I hope is usefull this example of base_convert-AS from decimal in 65imal base for a speedCode.
Some more specifical: you can transform using a db
$speedCodeDEC            = $idAziendaMittente.$idAziendaDestinatario.$idDDT ;

//$speedCodeDEC = 3000;

//
$BASECODE = array();
$BASECODE['items'] = 65;
$BASECODE[1]='1';
$BASECODE[2]='2';
$BASECODE[3]='3';
$BASECODE[4]='4';
....
$BASECODE[10]='a';
$BASECODE[11]='b';
$BASECODE[12]='c';
...
$BASECODE[36]='A';
$BASECODE[37]='B';
$BASECODE[38]='C';
...
$BASECODE[61]='Z';
$BASECODE[62]='/';
$BASECODE[63]='-';
$BASECODE[64]='+';
//

//print_r ($BASECODE);TEST

function creaSpeedCode ( $speedCodeDEC,$partialCode="",$BASECODE){

    @$division      = $speedCodeDEC/$BASECODE['items'];
    @$resultINT   = floor($speedCodeDEC/$BASECODE['items']);
    @$remnant          = $speedCodeDEC%$BASECODE['items'];
    $partialCode  = $BASECODE[$remnant].$partialCode;
echo "
    <br>
    Inserito speedCodeDEC:$speedCodeDEC - partialCode:$partialCode<br>
    items            : ".$BASECODE['items']."<br>
    division          : $division    <br>
    resultINT        : $resultINT    <br>
    remnant            : $remnant        <br>
    partialCode        : $partialCode    <br>
";//TEST   
    if ($resultINT > 65)     $partialCode = creaSpeedCode($resultINT,$partialCode,$BASECODE);
    return $BASECODE[$resultINT].$partialCode;
}
echo $speedCodeDEC."<br>";
echo $risultato = creaSpeedCode ( $speedCodeDEC,"",$BASECODE);
Theriault 30-Nov-2009 02:11
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.
cyrilbele at yahoo dot fr 16-Apr-2009 01:58
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;
}
?>
Ray Paseur sometimes uses GMail 06-Dec-2006 03:55
[EDIT BY danbrown AT php DOT net: This function provides conversion of Arabic numerals (those used by most of the world, the standard 1,2,3,4,...) into Roman numerals (I,II,III,IV,...).  The original author failed to provide a description, but due to the usefulness of the function, it is being preserved from deletion, and a simple description added.]

<?php
function roman_numerals($input_arabic_numeral='') {

    if (
$input_arabic_numeral == '') { $input_arabic_numeral = date("Y"); } // DEFAULT OUTPUT: THIS YEAR
   
$arabic_numeral            = intval($input_arabic_numeral);
   
$arabic_numeral_text    = "$arabic_numeral";
   
$arabic_numeral_length    = strlen($arabic_numeral_text);

    if (!
ereg('[0-9]', $arabic_numeral_text)) {
return
false; }

    if (
$arabic_numeral > 4999) {
return
false; }

    if (
$arabic_numeral < 1) {
return
false; }

    if (
$arabic_numeral_length > 4) {
return
false; }

   
$roman_numeral_units    = $roman_numeral_tens        = $roman_numeral_hundreds        = $roman_numeral_thousands        = array();
   
$roman_numeral_units[0]    = $roman_numeral_tens[0]    = $roman_numeral_hundreds[0]    = $roman_numeral_thousands[0]    = ''; // NO ZEROS IN ROMAN NUMERALS

   
$roman_numeral_units[1]='I';
   
$roman_numeral_units[2]='II';
   
$roman_numeral_units[3]='III';
   
$roman_numeral_units[4]='IV';
   
$roman_numeral_units[5]='V';
   
$roman_numeral_units[6]='VI';
   
$roman_numeral_units[7]='VII';
   
$roman_numeral_units[8]='VIII';
   
$roman_numeral_units[9]='IX';

   
$roman_numeral_tens[1]='X';
   
$roman_numeral_tens[2]='XX';
   
$roman_numeral_tens[3]='XXX';
   
$roman_numeral_tens[4]='XL';
   
$roman_numeral_tens[5]='L';
   
$roman_numeral_tens[6]='LX';
   
$roman_numeral_tens[7]='LXX';
   
$roman_numeral_tens[8]='LXXX';
   
$roman_numeral_tens[9]='XC';

   
$roman_numeral_hundreds[1]='C';
   
$roman_numeral_hundreds[2]='CC';
   
$roman_numeral_hundreds[3]='CCC';
   
$roman_numeral_hundreds[4]='CD';
   
$roman_numeral_hundreds[5]='D';
   
$roman_numeral_hundreds[6]='DC';
   
$roman_numeral_hundreds[7]='DCC';
   
$roman_numeral_hundreds[8]='DCCC';
   
$roman_numeral_hundreds[9]='CM';

   
$roman_numeral_thousands[1]='M';
   
$roman_numeral_thousands[2]='MM';
   
$roman_numeral_thousands[3]='MMM';
   
$roman_numeral_thousands[4]='MMMM';

    if (
$arabic_numeral_length == 3) { $arabic_numeral_text = "0" . $arabic_numeral_text; }
    if (
$arabic_numeral_length == 2) { $arabic_numeral_text = "00" . $arabic_numeral_text; }
    if (
$arabic_numeral_length == 1) { $arabic_numeral_text = "000" . $arabic_numeral_text; }

   
$anu = substr($arabic_numeral_text, 3, 1);
   
$anx = substr($arabic_numeral_text, 2, 1);
   
$anc = substr($arabic_numeral_text, 1, 1);
   
$anm = substr($arabic_numeral_text, 0, 1);

   
$roman_numeral_text = $roman_numeral_thousands[$anm] . $roman_numeral_hundreds[$anc] . $roman_numeral_tens[$anx] . $roman_numeral_units[$anu];
return (
$roman_numeral_text);
}
?>
CJ Dennis 06-Apr-2006 01:03
Really huge numbers might be truncated at both ends.
eg:
<?php
$binary
="11010101001111010001110101000100011110010110110".
"001111000010001010001111001100011010110110010010011010".
"001011010000001001011111110001010101101101011010101010".
"000100011101110010110010100111110001010010111010110011".
"001111111100011001011011001110001111110000101011010010";
print(
strtoupper(base_convert($binary, 2, 16)));
?>
will output:
9E8EA23CB63C0000000000000000000000000000000000000000000000000000 (64 hex digits)
when the correct result would be:
6A9E8EA23CB63C228F31AD9268B4097F156D6AA11DCB29F14BACCFF196CE3F0AD2 (66 hex digits)
Notice that as well as the result showing '0's after B63C which you would expect it is also missing the first 6A before 9E.
lindsay at bitleap dot com 18-Mar-2005 01:17
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 );
}

?>
simon at simonster dot com 15-Jun-2004 06:05
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.
AdamJacobMuller at AdamJacobMuller dot com 28-Apr-2004 02:20
<?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
fiftytoo at buckeyeexpress dot com 24-Dec-2003 12:57
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

?>