Access Control Modifier in PHP

Introduction

The access modifier is the most important feature of the OO language and it is used to restrict the function and classes to be accessed. The list of the access modifiers are:

• Public
  Class properties and methods, that are set to be public, can be accessed anywhere in the PHP script, in other words everywhere.
   
• Private
  Class properties and methods, that are set to be private, can only be accessed within a class, in other words only in which it is defined.
   
• Protected
  Class properties and method, that are set to be protected, can only be accessed inside the class and by its subclasses, in other words its class and sub classes.

For a better understanding of Access Control modifiers in PHP, I have created a table structure to show them.

means access allow.

 means access Not allow.

Modifier Name	Within Class	Out Side Class	After Inheritance
Public
Private
Protected

Simple Example of access controls

<?php

class className

{

//delaere variables with access modifier

public $variableName;

private $variableName;

protected $variableName;

 

//public method

public MethodName()

{

//body

}

//private method

private MethodName()

{

//body

}

protected MethodName()

{

//body

}

}

?>

Now each and every one, one by one.

Public access modifier

It is quite clear, the "public" access modifier achieves the highest level of accessibility. If you define your class properties and methods as "public", then it can be used anywhere in your PHP script.
 

Example of Public access modifier

In the following example, the class property and method of Myclass is set to be "public", and outside the class, an instance is created of Myclass. Then the "title" property is accessed by $obj and is assigned a "title" "ABCXYZ". Then the value of the title property is "$obj".

An instance is accessed again to display it, and finally the class method disptitle() is called by $obj, that will also display the value of the "title" property of the instance of the class. Since this method has an access to the title property, this is happening because of the class property and the method is public.  

<?php

class Myclass

{

public $title;

 

public function DispTitle()

{

echo $this -> title;

echo "<br />";

}

}

$obj = new Myclass();

$obj->title = "ABCXYZ";

echo $obj->title;

echo "<br />";

echo $obj->DispTitle();

?>

Output

Private access modifier

It is quite clear, if you declare any variables or methods in PHP as private, then they can only be used inside the class. You cannot call the private method using the class object.

Example of Private access modifier

In the following example, the "title" property is set to be private, which means you cannot access it directly outside of this class by using its instance. Suppose you try to access $title for an instance $obj by using $obj->title; then it will generate an error. To solve this problem, here we define two public methods, the function "SetTitle()" sets the value in the "title property" and the function "DispTitle()" displays the "title" value.

<?php

class Myclass

{

private $title;

public function SetTitle($setval)

{

$this->title=$setval;

}

public function DispTitle()

{

echo $this -> title;

echo "<br />";

}

}

$obj = new Myclass();

$obj->SetTitle("ABCXYZ");

$obj->DispTitle();

?>

Output

protected access modifier

When you declare the property and method with this keyword, you can access these methods and properties within the class, or/and the child class of that parent class can access these properties and methods of the parent class.

Example

<?php
class Myclass
{
protected $title=10;
}
class Baseclass extends Myclass
{
function __construct()
{
echo $this->title;
}
}
$obj = new Baseclass();
?>

Output