Basic knowledge of PHP: classes and objects (4) range resolution operator (::)_PHP tutorial

WBOY
Release: 2016-07-21 15:59:20
Original
1143 people have browsed it

The scope resolution operator (also known as Paamayim Nekudotayim) or more simply a pair of colons can be used to access static members, methods and constants, and can also be used to access members and methods in overridden classes.
When accessing these static members, methods and constants outside the class, the class name must be used.
Paamayim Nekudotayim means double colon in Hebrew.

Use :: operator outside the class
class MyClass {
const CONST_VALUE = 'A constant value';
}

echo MyClass::CONST_VALUE;

The two special keywords self and parent are used to access members or methods inside the class.

Example:
class OtherClass extends MyClass
{
public static $my_static = 'static var';

public static function doubleColon() {
echo parent ::CONST_VALUE . " n";
echo self::$my_static . " n";
}
}
OtherClass::doubleColon();

When a subclass When overriding a method in its parent class, PHP will no longer execute the overridden methods in the parent class until these methods are called in the child class. (Is it nonsense? No, this is a little difference between PHP and other mainstream languages). This mechanism also works for constructors and destructors, overloads, and magic functions.

class MyClass
{
protected function myFunc() {
echo "MyClass::myFunc() n";
}
}

class OtherClass extends MyClass
{
// Override the method in the parent class
public function myFunc()
{
// But you can still call the overridden method
parent:: myFunc();
echo "OtherClass::myFunc() n";
}
}

$class = new OtherClass();
$class->myFunc( );




--------------------------------- -----------------------------------------------
??Important??When accessing static methods or members, you must use the class name:: method.
Another note: PHP will not actively call the methods of the parent class, including constructors and destructors.
See this text: http://163xiaofan.blog.163.com/blog/static/1713578020061027101820973

www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/317404.htmlTechArticleThe range resolution operator (also known as PaamayimNekudotayim) or more simply a pair of colons can be used Access static members, methods and constants, and can also be used to access overridden classes...
source:php.cn
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template