Base conversion of arbitrary sized numbers (PHP)

Question

I have a long \"binary string\" like the output of PHPs pack function.

How can I convert this value to base62 (0-9a-zA-Z)? The built in maths functions overflow with

Answer 1

Unless you really, really have to have base62, why not go for:

base64_encode()
base64_decode()

The only other added characters are "+" and "=", and it's a very well-known method to pack and unpack binary strings with available functions in many other languages.