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:

<code class="php">// 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;</code>

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