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russell dot s dot harper at gmail dot com ¶

15 years ago

A gotcha when using the value from gmp_strval as a key in an associative array. Some numbers are 2^31 are converted to signed integer format, this is usually incorrect.

<?php

$a = gmp_init('2147483649'); // = 2^31 + 1
$b = gmp_init('3173604585'); // = 2^31 < $b < 2^32 

$c = gmp_strval($a);
$d = gmp_strval($b);

$e = array($c => 'c', $d => 'd');

print '*** Expect '."\n";
print 'Array '."\n".'('."\n".'    ['.$c.'] => c'."\n".'    ['.$d.'] => d'."\n".')'."\n\n";
print '*** Actual '."\n";
print_r($e);

?>

Output:

*** Expect
Array
(
    [2147483649] => c
    [3173604585] => d
)

*** Actual
Array
(
    [-2147483647] => c
    [3173604585] => d
)

A workaround is to format as base 16 and append '0x' before using as a key.

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