The following script gives the wrong answer:

<?php
$var1 = 3232300816;
$var2 = 256;
$var3 = $var1 % $var2;
print "$var1 % $var2 = $var3";
?>

Output is:

3232300816 % 256 = 0

Correct answer is 16.  This appears to be a consistent error, perhaps above the maximum for a 32-bit signed int?

Documentation doesn't seem to describe the limits, but this is all 32-bit.