If you need to do math operations with very large numbers you need bcmath. From the
manual :
http://www.php.net/manual/ref.bc.php3
Arbitrary precision mathematics functions
These functions are only available if PHP was configured with --enable-bcmath.
Table of Contents
bcadd - Add two arbitrary precision numbers.
bccomp - Compare two arbitrary precision numbers.
bcdiv - Divide two arbitrary precision numbers.
bcmod - Get modulus of an arbitrary precision number.
bcmul - Multiply two arbitrary precision number.
bcpow - Raise an arbitrary precision number to another.
bcscale - Set default scale parameter for all bc math functions.
bcsqrt - Get the square root of an arbitray precision number.
bcsub - Subtract one arbitrary precision number from another.
