php constructor

Starting from php5, you can declare the __construct constructor method in the class. When the object is instantiated, this method is called.
Note:
1. If there is no constructor method in the inherited subclass but there is a constructor method in the parent class, then when the subclass is instantiated, the constructor method of the parent class will be called implicitly.
2. If the subclass has a constructor and the parent class also has a constructor, then the subclass must explicitly call parent::__construct() to access the parent class's constructor.
3. For forward compatibility, if the __construct() method is not found in the php5 class, it will look for a constructor with the same method name as the class name.

class Person{
public $sex = '男';
function __construct() {
echo 'parent __construct';
}
}
class Student extends Person{
private $id;
private $name;
private $age;
//构造函数
function __construct($id,$name,$age) {
parent::__construct();
echo '__construct';
$this->id = $id;
$this->name = $name;
$this->age = $age;
}
public function getName() {
return $this->name;
}
//析构函数
function __destruct(){
echo '__destruct';
}
}
$su = new Student('id001','张三',20);
echo $su->getName();
echo $su->sex;

Print result:

parent __construct
__construct
Zhang San
Male
__destruct