PHP构造函数的执行顺序

PHP构造函数的执行顺序

测试代码如下：

<?php
class grandfather {
    public function __construct(){
        echo 'grandfather';
    }
}
class father extends grandfather {
    public function __construct(){
        echo 'father';
    }
}
class son extends father {
    public function __construct(){
        echo 'son';
    }
}
$test = new son();

结果是 :   son

<?php
class grandfather {
    public function __construct(){
        echo 'grandfather';
    }
}
class father extends grandfather {
    public function __construct(){
        echo 'father';
    }
}
class son extends father {
    
}
$test = new son();

结果： father

<?php
class grandfather {
    public function __construct(){
        echo 'grandfather';
    }
}
class father extends grandfather {

}
class son extends father {
    
}
$test = new son();

结果：grandfather

由此可见php类的构造函数调用是 从自身向上查找，执行最近的一个，然后stop