I have a couple of classes, and certain classes require only a part of an SDK. For example class a { /* requires filea.php*/ } class b { /*requires fileb.php*/ } Instead of including the files at the top like require_once 'filea.php'; require_once 'fileb.php'; class a { /*do stuff*/ } class b { /*do stuff*/ } Can I just include them in the class, so one only loads when an object is made? class a { require filea.php; /*do stuff*/ } class b { require fileb.php; /*do stuff*/ }