Trimming hashed password (for user identification)

Question

Question by GARR

as you can see at the bottom I am using hash as a way to identify users. How can I trim off the rest after 10 characters?

Answer 1

Trimming runs the risks of hash collisions where two users potentially share the same trimmed portion.

Hashing algorithms go to great length to avoid this possibility so modification of the hashed results in any way is not recommended.

Answer 2

$hash = substr($hash,0,10);