How to access a private member inside a static function in PHP

Question

I have the following class in PHP

class MyClass
{
  // How to declare MyMember here? It needs to be private
  public static function MyFunction()
  {
    // How to access MyMember here?
  }
}

I am totally confused about which syntax to use

$MyMember = 0; and echo $MyMember

or

private $MyMember = 0; and echo $MyMember

or

$this->MyMember = 0; and echo $this->MyMember

Can someone tell me how to do it?

I am kind of not strong in OOPS.

Can you do it in the first place?

If not, how should I declare the member so that I can access it inside static functions?

Answer 1

class MyClass
{
  private static $MyMember = 99;

  public static function MyFunction()
  {
    echo self::$MyMember;
  }
}

MyClass::MyFunction();

see Visibility and Scope Resolution Operator (::) in the oop5 chapter of the php manual.

Answer 2

Within static methods, you can't call variable using $this because static methods are called outside an "instance context".

It is clearly stated in the PHP doc.

Answer 3

<?php
    class MyClass
    {
        // A)
        // private $MyMember = 0;

        // B)
        private static $MyMember = 0;

        public static function MyFunction()
        {
            // using A) //  Fatal error: Access to undeclared static property: 
            //              MyClass::$MyMember
            // echo MyClass::$MyMember; 

            // using A) // Fatal error: Using $this when not in object context
            // echo $this->MyMember; 

            // using A) or B)
            // echo $MyMember; // local scope

            // correct, B) 
            echo MyClass::$MyMember;
        }
    }

    $m = new MyClass;
    echo $m->MyFunction();
    // or better ...
    MyClass::MyFunction(); 

?>