Question

I saw some codes that when they call php functions from another class they no longer use $this->functionName(),
they just refer immedietly to the function name, like functionName()

In my index.php

 $help = new Helper();
 $help->Test();

I wanted to call Test Function by not doing the $help.

How can this be done? Why is this possible?

Answer 1

In PHP you can mix a procedural style of programming with object oriented style. That means that function can either exist as member of a class, or as stand-alone functions.

Member functions (or methods) are are called using $classinstance->methodname() for normal (instance) methods, or ClassName::methodName() for static methods.

Standalone functions are just called without referring to a class or object whatsoever. You can put them in separate files, if you like.
The declaration and usage is as follows:

In example.php:

class MyClass
{
  $member = 'Hello world';

  function MyMethod()
  {
    // The method can use the instance variable (member variable) 
    // using $this to refer to the instance of the class
    echo $this->member;  
  }

  static function MyStaticMethod()
  {
    echo 'Hello static world';
  }

}

function MyFunction()
{
  echo 'Hello';
}

In index.php:

// To include the class and its methods, as well as the function.
require_once 'example.php';

// Call an instance method
$instance = new MyClass();
$instance->MyMethod();

// Call a static method
MyClass::MyStaticMethod();

// Call a stand-alone function
MyFunction();