Update 'classes/tools.class.php'

classes/tools.class.php

   */
   public static function check_cidr_range($CheckIP, $Subnet) {
     $IP = ip2long($CheckIP);
-    $CIDR = split('/', $Subnet);
+    $CIDR = preg_split('/', $Subnet);
     $SubnetIP = ip2long($CIDR[0]);
     $SubnetMaskBits = 32 - $CIDR[1];