PHP/MySQL: Storing and retrieving UUIDS

Question

I'm trying to add UUIDs to a couple of tables, but I'm not sure what the best way to store/retrieve these would be. I understand it's far more efficient to use BINARY(16) instead of VARCHAR(36). After doing a bit of research, I also found that you can convert a UUID string to binary with:

 UNHEX(REPLACE(UUID(),'-',''))

Pardon my ignorance, but is there an easy way to this with PHP and then turn it back to a string, when needed, for readability?

Also, would it make much difference if I used this as a primary key instead of auto_increment?

EDIT:

Found part of the answer:

 $bin = pack("h*", str_replace('-', '', $guid));

How would you unpack it?

Answer 1

Okay -- going to try to answer my own question. This is the best I could come up with:

Pack:

$binary =  pack("h*", str_replace('-', '', $string));

Unpack

$string = unpack("h*", $binary);
$string = preg_replace("/([0-9a-f]{8})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{12})/", "$1-$2-$3-$4-$5", $string);

Is there any problem with this anyone can see?