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*/ }