<?php
function guidv4($data = null) {
// Generate 16 bytes (128 bits) of random data or use the data passed into the function.
$data = $data ?? random_bytes(16);
assert(strlen($data) == 16);
// Set version to 0100
$data[6] = chr(ord($data[6]) & 0x0f | 0x40);
// Set bits 6-7 to 10
$data[8] = chr(ord($data[8]) & 0x3f | 0x80);
// Output the 36 character UUID.
return vsprintf('%s%s-%s-%s-%s-%s%s%s', str_split(bin2hex($data), 4));
}
print guidv4;