Define a class

 class p {
    function p() {
        print "Parent's constructor\n";
    }  
    function p_test() {
        print "p_test()\n";
        $this->c_test();
    }
 }
 class c extends p {
    function c() {
        print "Child's constructor\n";
        parent::p();
    }  
    function c_test() { 
        print "c_test()\n";
    }
 }
 $obj = new c;
 $obj->p_test();