php does not call the parent class

Inheritance in PHP is a very powerful feature, which allows subclasses to inherit the properties and methods of the parent class, avoiding the problem of repeatedly writing code. In the actual development process, we often need to rewrite parent class methods in subclasses to meet specific needs. But sometimes we don’t need to call the parent class’s method. How should we deal with it?

In PHP, when we override a method, we do not have to call the method of the parent class. If we implement a method with the same name in a subclass, this method will override the method with the same name in the parent class. If we need to use the method of the parent class, we can use the following two methods:

1. Use the parent keyword to call the parent class method

When we override it in the subclass A method, you can use the parent keyword to call the method of the parent class. The specific implementation method is as follows:

class ParentClass {
    public function func() {
        echo 'ParentClass';
    }
}

class SubClass extends ParentClass {
    public function func() {
        parent::func();
        echo 'SubClass';
    }
}

$obj = new SubClass();
$obj->func();  // 输出：ParentClass SubClass

In the above code, we first define a parent class ParentClass and a subclass SubClass. The subclass SubClass inherits from the parent class ParentClass. We override the parent class method func() in the subclass, and use the parent::fun() statement to call the parent class method. When we run $obj->func(), the method content of the parent class will be output first, and then the method content of the subclass will be output.

2. Not using the parent keyword

If we override a method in a subclass, but do not need to use the method content of the parent class, then we can also not Use the parent keyword. The specific implementation method is as follows:

class ParentClass {
    public function func() {
        echo 'ParentClass';
    }
}

class SubClass extends ParentClass {
    public function func() {
        echo 'SubClass';
    }
}

$obj = new SubClass();
$obj->func();  // 输出：SubClass

The above code is similar to the previous code, except that when rewriting the parent class method in the subclass, the parent::fun() statement is not used to call the parent class method. When we run $obj->func(), only the method content of the subclass will be output, and the method content of the parent class will not be output.

It should be noted that if we rewrite the constructor of the parent class in the subclass, we must call the constructor of the parent class in the constructor of the subclass, otherwise the subclass object cannot be generated. The specific implementation method is as follows:

class ParentClass {
    public $name;

    public function __construct($name) {
        $this->name = $name;
    }
}

class SubClass extends ParentClass {
    public function __construct($name) {
        parent::__construct($name);
    }
}

$obj = new SubClass('Tom');
echo $obj->name;  // 输出：Tom

In the above code, we first define a parent class ParentClass and a subclass SubClass. The subclass SubClass inherits from the parent class ParentClass. We rewrite the constructor of the parent class in the subclass and call the constructor of the parent class using the parent::__construct($name) statement. When we generate the subclass object $obj, the constructor of the subclass will be called, and the constructor of the parent class will be called through parent::__construct($name) to assign values ​​to the subclass attributes. Finally, we output the subclass's attribute value $obj->name, which turns out to be 'Tom'.

In summary, when we override the parent class method in a subclass, if we need to use the parent class's method content, we can use the parent keyword to call the parent class's method; if we do not need to use the parent class's method content, Method content, you can directly override the method in the subclass. Either way, the problem of calling parent class methods is handled well.

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