PHP Unconference Europe 2015

gmp_cmp

(PHP 4 >= 4.0.4, PHP 5)

gmp_cmpCompare numbers

Description

int gmp_cmp ( GMP $a , GMP $b )

Compares two numbers.

Parameters

a

Either a GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric string provided that it is possible to convert the latter to a number.

b

Either a GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric string provided that it is possible to convert the latter to a number.

Return Values

Returns a positive value if a > b, zero if a = b and a negative value if a < b.

Examples

Example #1 gmp_cmp() example

<?php
$cmp1 
gmp_cmp("1234""1000"); // greater than
$cmp2 gmp_cmp("1000""1234"); // less than
$cmp3 gmp_cmp("1234""1234"); // equal to

echo "$cmp1 $cmp2 $cmp3\n";
?>

The above example will output:

1 -1 0
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User Contributed Notes 1 note

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russell dot harper at springboardnetworks dot com
4 years ago
I've encountered a memory leak in gmp_cmp if a literal string is used as the second value inside of loops. A workaround is to initialize first, then use the variable. I wasn't able to generate a minimum code sample, it's something more complicated, but I was able to fix it as follows:

<?php

$x
= gmp_init(strval(mt_rand()));

// Depending on surrounding code, may have leaks
while (true)
{
    if (!
gmp_cmp($x, '1'))
        print
'one'."\n";
}

// Usually doesn't have leaks
$one = gmp_init('1');

while (
true)
{
    if (!
gmp_cmp($x, $one))
        print
'one'."\n";
}

?>
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