no more need to use ldap_get_values_len (). ldap_get_attributes() works well now.
<?php
$attrs = ldap_get_attributes($this->cid, $this->re);
$hex_Sid= bin2hex($attrs['objectSid'][0]); //returns 010500000000000515000000c94d7d363d787b17e77b80109d060000
$hex_GUID= bin2hex($attrs['objectGUID'][0]); //returns 710234bbc2abc148ade8c1f9b4567b24
?>