PHP static and const keyword usage Analysis _php tips

This example describes the static and const keyword usages in PHP. Share to everyone for your reference, specific as follows:

The member properties and member functions that the static keyword describes in the class are static.

A static member can restrict external access because the static member belongs to the class, not to any object instance.

From the memory point of view, where the object is placed in "heap memory", the object's reference is placed in "stack memory", while the static member is placed in the initialization static segment, when the class is first loaded. Lets you share all the objects in memory. As shown in the following illustration:

<?php
class person{public
 static $myCountry = "China";
 public static function say () {
  echo "My Motherland is:". Self:: $myCountry. <br> ";
 }
}
Output static properties
echo Person:: $myCountry. " <br> ";
Call static method
Person::say ();
Modify static Properties Person
:: $myCountry = "China-Jiangsu";
echo Person:: $myCountry. " <br> ";
? >

The output results are:

My Motherland in China is: China
-Jiangsu

Static methods in a class can only access static properties of a class. A static method in a class cannot access a non-static member of a class. We use self to access static properties in a class. Self is similar to this, except that self represents the class where the static method is located, this is similar, except that self represents the class in which the static method is located, this reference pointer, which represents the object that called the method. The static method is not called by the object, and there is no this reference. There is no this reference to this. Without this, there is no way to invoke other member properties in the class.

Const is a keyword that defines a constant. Use const in a class to define constants. Member properties that are decorated with "const" are accessed in much the same way as members accessed by the "static" modifier, using "class name" and the "self" keyword in the method. However, you do not use the "$" symbol, and you cannot use objects to access it.

<?php
class myclass{
 Const constant = ' constant value ';
 function Showconstant () {
  //method calls constants, no $
  echo self::constant. " <br> ";
 }
}
Class is called directly, without the $
echo myclass::constant. " <br> ";
$class = new MyClass ();
$class->showconstant ();
? >

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