fastest way to hash a string in an int

[eluser]gungbao[/eluser]
Hi Coders,

I am looking for PHPs fastest way to convert a string of an arbitrary length into ... not an md5 but a positive integer, not a unique one but the same string needs to end up always to the same integer. lets say, similar to md5 but without any characters but only digits in the hash.

Anyone an idea for a solution faster than grepping/replacing all numbers from a resulting md5?

Have fun to think about it would help me a lot.
Thanks in advance for any idea,
Chris