PHP var becoming negative

Question

I have this code :

<?php
$integer = 33963677451;
$integer &= 0xFFFFFFFF;
echo $integer;
?>

But, when I execute it, the output is

-396060917

The same function in Python

if __name__ == '__main__':
    integer = 33963677451
    integer &= 0xFFFFFFFF
    print integer

The output is

3898906379

It seems PHP can't store big variables. Do you guys have any idea how to get the same result in PHP I have in Python ?

Thanks !

Answer 1

That value is too big for an integer, python dynamically casts that into a long variable. INT_MAX defines how big your integer can be before it switches over into a double. If you want to manipulate large numbers without quirks use GMPLIB a multiple precision arithmetic library.

Answer 2

Your 33,963,677,451 is above what a signed 32bit integer supports (max 2,147,483,647). 64bit PHP versions do support higher values.

Answer 3

php only supports signed integers. You are seeing overflow

also, the answer for the python case should be 33963677451

Answer 4

I don't know if it's just a typo, but you are using different values when performing the AND operation in each language. :)

You have "0xFFFFFFFFFFF" (11 chars) in your PHP version, as opposed to only 8 in the Python version.

Either way, it should be integer overflow.

Answer 5

<?php
$integer = (float) 33963677451;
$integer &= 0xFFFFFFFFFFF;
echo $integer;

try making sure that $integer is of type float.

for more: http://www.php.net/manual/de/language.types.integer.php#language.types.integer.overflow

Answer 6

If you wish to see whats happening, here is a printf statement showing the different types.

$i1 = 33963677451;
$i2 = 0xFFFFFFFFFFF;
printf("%b (%d, %f) & \n%b (%d, %f)\n = \n%b (%d, %f)", 
        $i1, $i1, $i1, $i2, $i2, $i2, $i1&$i2, $i1&$i2, $i1&$i2);

PHP casts integers larger than 32 bits to floats. It seems that you can not perform this operation on floats.