PHP 5.6.0RC3 is available

gmp_init

(PHP 4 >= 4.0.4, PHP 5)

gmp_initCreate GMP number

Description

GMP gmp_init ( mixed $number [, int $base = 0 ] )

Creates a GMP number from an integer or string.

Parameters

number

An integer or a string. The string representation can be decimal, hexadecimal or octal.

base

The base.

The base may vary from 2 to 36. If base is 0 (default value), the actual base is determined from the leading characters: if the first two characters are 0x or 0X, hexadecimal is assumed, otherwise if the first character is "0", octal is assumed, otherwise decimal is assumed.

Return Values

A GMP number resource in PHP 5.5 and earlier, or a GMP object in PHP 5.6 and later.

Changelog

Version Description
5.3.2 The base was extended from 2 to 36, to 2 to 62 and -2 to -36.
4.1.0 The optional base parameter was added.

Notes

Note:

To use the extended base introduced in PHP 5.3.2, then PHP must be compiled against GMP 4.2.0 or greater.

Examples

Example #1 Creating GMP number

<?php
$a 
gmp_init(123456);
$b gmp_init("0xFFFFDEBACDFEDF7200");
?>

Notes

Note:

It is not necessary to call this function if you want to use integer or string in place of GMP number in GMP functions, like gmp_add(). Function arguments are automatically converted to GMP numbers, if such conversion is possible and needed, using the same rules as gmp_init().

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User Contributed Notes 6 notes

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0
marcus at synchromedia dot co dot uk
2 years ago
I discovered that the gmp functions use [0-9a-f] up to base 16, but [0-9A-Za-z] (i.e. upper case first) from bases 17 to 62. This differs from most of the base-62 implementations I've found that tend to use lower case first.
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0
karl dot debisschop at pearson dot com
3 years ago
Unless the base is 16, gpm_init will fail if the string begins with "0b".

> php -r '$v = gmp_init("b83", 17); print("$v\n");'

Resource id #4

> php -r '$v = gmp_init("0b83", 17); print("$v\n");'

[nothing prints]

In may case, where I am explicitly specifying the base, the solution is to apply ltrim first:

> php -r '$v = gmp_init(ltrim("0b83", "0"), 17); print("$v\n");'

Resource id #4
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0
charlie at oblivion dot cz
7 years ago
gmp_* functions don't accept strings with a leading '+':
<?php
echo gmp_strval(gmp_init('+42'));      #0
echo gmp_strval(gmp_add('42', '+42')); #42
echo bcadd('+42', '+42');              #84
?>
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0
php at richardneill dot org
7 years ago
Here's a way to parse a decimal (eg 3.25) into an integer and exponent:

<?
if (preg_match("/^[0-9]+\.[0-9]+$/",$input)){
    
//Input is a base-10 decimal. Multiply as necessary to remove the decimal
     //point. Convert that to a gmp_resource, then decrement the exponent
     //to compensate.

    
$pieces=explode(".", $input);     //Split at the d.p.
    
$input="$pieces[0]$pieces[1]"//Remove the decimal point.

    
$input=ltrim($input,'0');   
    
//Remove any leading zeros, or gmp_init will parse the number as octal.

    
if ($input==''){    //Deal with "0.0" which would otherwise be ''.
         
$input=0;
      }
     
$integer=gmp_init($input);  
     
$ns_exponent=-strlen($pieces[1]); 
    
//exponent = (-)  the number of characters after the decimal point.
}
?>
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0
php at richardneill dot org
7 years ago
Note: Leading zeros will make gmp_init parse this as octal.
Thus gmp_init(010) becomes 8. 

$a=010;              //8
$b="010" + 0;     //10
$c=gmp_strval(gmp_init(010));    //8
$d=gmp_strval(gmp_init("010")); //8

This behaviour is inconsistent: either $d should equal $b, or
$b should equal $a.
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-1
thomas dot hebinck at digionline dot de
8 years ago
If you call a gmp_* function directly with an interger as parameter, this integer MUST NOT be 0:

for($i=-1;$i<=1;$i++) {  echo gmp_strval(gmp_add(2,gmp_mul(1,$i))) . ' ';  }

The result is 1 0 3 (wrong)

In this case you have to use gmp_init():

for($i=-1;$i<=1;$i++) {  echo gmp_strval(gmp_add(2,gmp_mul(1,gmp_init($i)))) . ' ';  }

The result is 1 2 3 (right)

Happy number crunching! :-)
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