Usage of double colon:: in PHP

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Double colon operator: that is, the scope-limited operator Scope Resolution Operator can access static, const and class Overridden properties and methods.

1. When calling static properties and static methods

::With- >The function is the same, but the objects used are different! ::Refer to static methods or properties in the class, and do not need to be instantiated!

Create a class, and create a static property $a and a static method b, as follows:

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1. #class test {

2. static public $a;

3. static public function b() {}

4. }

If you want to call the static property $a, as follows

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1. #test::$a;

Note that a needs to be preceded by a $ sign, which is different from the -> sign!

If you want to call static method b, as follows

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##test::b();

##2. When calling the properties or methods of the own class or the parent class

First create a parent class

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1. ##class test {

2. public function b () {}

3. }

Then create a subclass inheritance father

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1. ##class

   tests extends test {

2. public function cs() {}

3. }

When we need to call method b of the parent class

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1. ##parent::b();

When we need When calling its own method cs, there are two methods

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#$this

1. ->cs();

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1. self::cs();  

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