What does :: mean in php
Double colon (::) is used in PHP for: 1. Namespace delimiter; 2. Static method call; 3. Parent class access; 4. Constant access; 5. Delayed static binding. For example, MyNamespace::MyClass represents the namespace delimiter, while MyClass::myStaticMethod() represents a static method call.
Double colon (::) in PHP
Double colon (::) in PHP has the following Purpose:
1. Namespace separator
- In PHP 5.3 and later versions, double colons are used to separate classes and functions in the namespace and constants.
- For example:
MyNamespace::MyClass
2. Static method call
- Double colon is available For calling static methods of a class without having to instantiate the class.
- For example:
MyClass::myStaticMethod()
##3. Parent class access
- Double The colon can be used to access the properties and methods of the parent class.
- For example:
- parent::myProperty
4. Constant access
- Double colon can be used Access the constants of a class without having to go through the class name.
- For example:
- MyClass::MY_CONSTANT
5. Delayed static binding (LSB)
- Double colons can be used to implement delayed static binding, allowing the method to be called to be determined at runtime.
- For example:
- static::myMethod()
Example:
// 命名空间分隔符 namespace MyNamespace; class MyClass {} // 静态方法调用 class Foo { public static function myStaticMethod() { echo "This is a static method.\n"; } } Foo::myStaticMethod(); // 父类访问 class Bar extends Foo { public function myChildMethod() { echo "This is a child method.\n"; parent::myStaticMethod(); } } $bar = new Bar(); $bar->myChildMethod(); // 常量访问 class Baz { const MY_CONSTANT = 'Hello, world!'; } echo Baz::MY_CONSTANT;
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