PHP object-oriented learning parent::keyword

<!-- 声明一个员工类,经理类继承自员工类 -->
<?
class employee{
 protected $sal=3000; 
 public function getSal(){
 $this->sal = $this->sal + 1200;
 return $this->sal ;
 }
}
  
class Manager extends employee {
 //如果想让经理在员工工资的基础上多发1500元.
 //必须先调用父类的getSal()方法.
 public function getSal(){ 
 parent::getSal();// 这里调用了父类的方法.
 $this->sal = $this->sal + 1500;
 return $this->sal ;
 }
}
$emp = new employee();
echo "普通员工的工资是 " . $emp->getSal();
echo "<br>";
//xiariboke.com
$manager = new Manager();
echo "经理的工资是: " . $manager->getSal();
?>

<?php
class employee{
 private $sal=3000;
 //protected $sal=3000;
 public function getSal(){ 
 return $this->sal;
 } 
}
  
class Manager extends employee {
 protected $sal=5000;
  
 public function getParentSal(){
 //这里返回的是父类的private属性.
 return parent::getSal();
 }
}
$manager = new Manager();
echo "PHP ".phpversion()."<br>";
echo $manager->getSal();
echo "<br>";
echo "parent&#39;s \$sal ".$manager->getParentSal();
//xiariboke.com
?>

<?php
class employee{
 //private $sal=3000;
 protected $sal=3000;
 public function getSal(){ 
 return $this->sal;
 } 
}
  
class Manager extends employee {
 protected $sal=5000;
 //xiariboke.com
 public function getParentSal(){
 //这里返回的是父类的private属性.
 return parent::getSal();
 }
}
$manager = new Manager();
echo "PHP ".phpversion()."<br>";
echo $manager->getSal();
echo "<br>";
echo "parent&#39;s \$sal ".$manager->getParentSal();
  
?>

<?php
class employee{
 private $sal=3000;
 public function getSal(){ 
 return $this->sal;
 }
}
  
class Manager extends employee {
 private $sal=5000;
 //重写过的方法
 public function getSal(){ 
 return $this->sal;
 } 
 public function getParentSal(){
 //这里返回的是父类的private属性.
 return parent::getSal();
 }
}
$manager = new Manager();
echo "PHP ".phpversion()."<br>";
echo $manager->getSal();
echo "<br>";
echo "parent&#39;s \$sal ".$manager->getParentSal();
  
?>

<?php
class employee{
 private $sal=3000;
 public function getSal(){ 
 return $this->sal;
 } 
}
class Manager extends employee {
 protected $sal=5000;
 public function getParentSal(){
 return $this->sal;
 }
}
$manager = new Manager();
echo "PHP ".phpversion()."<br>";
echo $manager->getSal();
  
?>

<?php
class employee{
 protected $sal=3000;
 public function getSal(){ 
 return $this->sal;
 } 
}
class Manager extends employee {
 protected $sal=5000;
 public function getParentSal(){
 return $this->sal;
 }
}
$manager = new Manager();
echo "PHP ".phpversion()."<br>";
echo $manager->getSal();
  
?>

<?php
class employee{
 private $sal=3000;
 public function getSal(){ 
 return parent::$this->sal;
 } 
}
  
class Manager extends employee {
 protected $sal=5000;
 public function getSal(){ 
 return parent::$this->getSal();
 }
}
$manager = new Manager();
echo "PHP ".phpversion()."<br>";
echo $manager->getSal();
  
?>