php继承与重载

<?php

    class A {
        public $param = "paramA";

        public function test() {
            echo "testA";
        }
    }

    class B extends A {
        public $param = "paramB";

        public function test() {
            echo "testB";
        }
    }

    $b = new B();
    echo "$b->param = " . $b->param . "<br>";
    $b->test();
?>

输出：

paramB = paramB
testB

也就是说，通过继承与重载，相同的变量和函数被子类覆盖。