In php is there a way to give a unique hash from a string, but that the hash was made up from numbers only?
example:
return md5(234); // returns 098f
First of all, md5 is basically compromised, so you shouldn't be using it for anything but non-critical hashing.
PHP5 has the hash() function, see http://www.php.net/manual/en/function.hash.php.
Setting the last parameter to true will give you a string of binary data. Alternatively, you could split the resulting hexadecimal hash into pieces of 2 characters and convert them to integers individually, but I'd expect that to be much slower.