<?php
class Alumn {
  private $name;
  private $mat;
  function getName()
  {
    return $this->name;
  }
  function getMat()
  {
    return $this->mat;
  }
}
 $a = new Alumn();
 if($a->getName() == NULL)
    print "Alumn->name is NULL\r\n";
 if($a->getMat() == NULL)
    print "Alumn->mat is NULL";
?>