Check to see that the LDAP extension is enabled before attempting to use it in the Unl_Ldap class.

library/Unl/Ldap.php

@@ -36,6 +36,10 @@ class Unl_Ldap {
      */
     public function __construct($uri)
     {
+        if (!function_exists('ldap_connect')) {
+            throw new Unl_Ldap_Exception('The PHP LDAP extension is required and is not enabled.');
+        }
+        
     	$this->_conn = ldap_connect($uri);
     	if($this->_conn === FALSE) {
     	    throw new Unl_Ldap_Exception('Could not connect to LDAP Server');