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phpstringbinarylimit

Exceed PHP binary limit

I was trying to do some sort of XOR binary crypting algorithm in PHP and so I needed to convert large strings into binary. The problem is that PHP seems to be very limited in terms of binary calculation / storage as a string of six letters only, once converted, exceeds the PHP INT limit.

That means unpacking a big string to binary just gives a unusable number. I tried to do the string unpacking by splitting the string into packs of 4 letters and then unpacking them, but then I've got troubles with the repacking where it gives random characters instead of the original ones.

How can I do the unpacking of very long strings, and then store them either in a string (made only of 0s and 1s) or in a big array (where each value is either a 0 or 1, the key indicating the location of this bit) ?

Solution

  • have you tried the GMP library? Man page GMP

    quick test code:

    <?php
$gmpValue1 = gmp_init("1562767628166296698262", 10); // note: using base 10 (decimal)
$gmpValue2 = gmp_init("2163623626362663286446", 10);

$gmpValue3 = gmp_xor($gmpValue1, $gmpValue2);

echo gmp_strval($gmpValue3, 10) . "\n"; // note: using base 10 (decimal)