How to call the variables and methods of the parent class in the PHP subclass

<? Phpclass A {public $ a1 = 'a1'; protected $ A2 = 'a2 '; function test () {echo "Hello! <HR/> ";}} Class B extends a {// if Class A and Class B are not in the same file, please include) public $ a1 = 'b1 '; function Test2 () {$ this-> test (); parent: Test (); // subclass calls the parent class method} function test () {echo $ this-> A1. ','; echo $ this-> A2 .','; echo "b2_test_hello <HR/>" ;}}$ A = new B (); $ A-> test (); // B1, A2, b2_test_hello $ A-> Test2 (); // B1, A2, b2_test_hello // Hello!?>

Method call: $ this-> method name (); if this method exists in the subclass, the method in the subclass is called. If not, the method in the parent class is called.

Parent: The method in the parent class is always called.

Variable call: $ this-> variable name. If this variable exists in the subclass, the variable is called in the subclass. If not, the variable is called in the parent class.