PHP class 继承

<?php
class ParentClass {
    private $name;
    private $age;
    public $local;
    public $hoby;
    public function __construct() {
        print "execute parent construct()<br/>";
        $this->setName ();
        echo ("name=" . $this->name . "<br/>");
        
        $this->setAge ();
        echo ("age=" . $this->age . "<br/>");
        
        $this->setLocal ();
        echo ("local=" . $this->local . "<br/>");
        
        $this->setHoby ();
        echo ("hoby=" . $this->hoby . "<br/>");
        $this->__toString();
    }
    private function setName() {
        $this->name = "parentName";
        print "parent setName()\n ";
    }
    public function setAge() {
        $this->age = 50;
        print "parent setAge()\n";
    }
    public function setLocal() {
        $this->local = "parent local";
        print "parent setLocal()\n";
    }
    private function setHoby() {
        $this->hoby = "parent hoby";
        print "parent setHoby()\n";
    }
    
    public function __toString() {
        echo ("Parent[name=" . $this->name . ", age=" . $this->age . ", local=" . $this->local . ", hoby=" . $this->hoby . "]<br>");
    }
}

?>

<?php
require_once ‘ParentClass.php‘;
class ChildClass extends ParentClass {
    private $name;
    private $age;
    public $local;
    public $hoby;
    public function __construct() {
        print "execute child construct()<br/>";
        parent::__construct ();
        echo $this->__toString();
    }
    private function setName() {
        $this->name = "childName";
        print "child setName()\n";
    }
    public function setAge() {
        $this->age = 20;
        print "child setAge()\n";
    }
    public function setLocal() {
        $this->local = "child local";
        print "child setLocal()\n";
    }
    private function setHoby() {
        $this->hoby = "child hoby";
        print "child setHoby()\n";
    }
    public function __toString() {
        echo ("Child[name=" . $this->name . ", age=" . $this->age . ", local=" . $this->local . ", hoby=" . $this->hoby . "]<br/>");
    }
}

$child = new ChildClass ();
?>