base_convert

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

base_convert — Converte un numero fra basi arbitrarie

Descrizione

base_convert(string $numero, int $base_di_partenza, int $base_di_arrivo): string

Restituisce una stringa contenente numero rappresentata in base base_di_arrivo. La base in cui numero è dato è specificata da base_di_partenza. Entrambe base_di_partenza e base_di_arrivo devono essere comprese fra 2 e 36, inclusi. Cifre in numeri con una base maggiore di 10 saranno rappresentati con le lettere a-z, con a significante 10, b significante 11 e z significante 35.

Example #1 Esempio di uso di base_convert()

<?php
$hexadecimal = 'A37334';
echo base_convert($hexadecimal, 16, 2);
?>

Visualizza:

101000110111001100110100

Avviso

La funzione base_convert() può perdere di precisione con numeri molto grandi a causa delle proprietà dei tipi "double" o "float" utilizzati internamente. Fare riferimento alla sezione Floating point numbers del manuale per informazioni specifiche e per le limitazione.

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User Contributed Notes 6 notes

down

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;
}
?>

down

ardavies at tiscali dot co dot uk ¶

11 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

down

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

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lindsay at bitleap dot com ¶

20 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 );
}

?>

down

ohcc at 163 dot com ¶

7 years ago

<?php
    $v = base_convert(3.14, 10, 10);
    var_dump($v);
?>

output: string(3) "314"

down

cyrilbele at yahoo dot fr ¶

16 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;

}

?>

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