Private Php

Private Php
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If some property or method is declared as a private visibility keyword in PHP, it can only be accessed within its class.
The Private function will only be accessed in the class in which it was defined and cannot be accessed out of class.
A major drawback of using the private function is that the child classes cannot inherit such functions; the private function should be used correctly.
Calling the function TestPrivate() outside the class:
Calling the function test() outside the class:
As we can see, when the private function only works when it is called inside its class, in our code, we created a public function test to call the private function so we can call it outside the class.
It is impossible to call a private method declared into a child class. Private methods can only be called in the same class.
The Class test_private2 is the child class of the test_private class given in the code in the first example. We called the parent class a private function into child class.
What if we override the private function by creating a new function with the same name in the child class? The answer to that is once a private function is declared, it cannot be overridden in child class.
The code above tries to override both private and public functions in the child class, but only the public function will be overridden.
As we can see from the output, the private function is not overridden from the child class.
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public ;        echo $this -> protected ;        echo $this -> private ;    } } $obj = new MyClass (); echo $obj -> public ; // Works echo $obj -> protected ; // Fatal Error echo $obj -> private ; // Fatal Error $obj -> printHello (); // Shows Public, Protected and Private /** * Define MyClass2 */ class MyClass2 extends MyClass {    // We can redeclare the public and protected properties, but not private    public $public = 'Public2' ;    protected $protected = 'Protected2' ;    function printHello ()    {        echo $this -> public ;        echo $this -> protected ;        echo $this -> private ;    } } $obj2 = new MyClass2 (); echo $obj2 -> public ; // Works echo $obj2 -> protected ; // Fatal Error echo $obj2 -> private ; // Undefined $obj2 -> printHello (); // Shows Public2, Protected2, Undefined ?>

MyPublic ();        $this -> MyProtected ();        $this -> MyPrivate ();    } } $myclass = new MyClass ; $myclass -> MyPublic (); // Works $myclass -> MyProtected (); // Fatal Error $myclass -> MyPrivate (); // Fatal Error $myclass -> Foo (); // Public, Protected and Private work /** * Define MyClass2 */ class MyClass2 extends MyClass {    // This is public    function Foo2 ()    {        $this -> MyPublic ();        $this -> MyProtected ();        $this -> MyPrivate (); // Fatal Error    } } $myclass2 = new MyClass2 ; $myclass2 -> MyPublic (); // Works $myclass2 -> Foo2 (); // Public and Protected work, not Private class Bar {    public function test () {        $this -> testPrivate ();        $this -> testPublic ();    }    public function testPublic () {        echo "Bar::testPublic\n" ;    }        private function testPrivate () {        echo "Bar::testPrivate\n" ;    } } class Foo extends Bar {    public function testPublic () {        echo "Foo::testPublic\n" ;    }        private function testPrivate () {        echo "Foo::testPrivate\n" ;    } } $myFoo = new Foo (); $myFoo -> test (); // Bar::testPrivate                 // Foo::testPublic ?>

foo (); // Public, Protected and Private work /** * Define MyClass2 */ class MyClass2 extends MyClass {    // This is public    function foo2 ()    {        echo self :: MY_PUBLIC ;        echo self :: MY_PROTECTED ;        echo self :: MY_PRIVATE ; // Fatal Error    } } $myclass2 = new MyClass2 ; echo MyClass2 :: MY_PUBLIC ; // Works $myclass2 -> foo2 (); // Public and Protected work, not Private ?>

foo = $foo ;    }    private function bar ()    {        echo 'Accessed the private method.' ;    }    public function baz ( Test $other )    {        // We can change the private property:        $other -> foo = 'hello' ;        var_dump ( $other -> foo );        // We can also call the private method:        $other -> bar ();    } } $test = new Test ( 'test' ); $test -> baz (new Test ( 'other' )); ?>

string(5) "hello"
Accessed the private method.

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User Contributed Notes 27 notes

INSIDE CODE and OUTSIDE CODE label = 'Ink-Jet Tatoo Gun' ; $item -> price = 49.99 ; ?> Ok, that's simple enough... I got it inside and out. The big problem with this is that the Item class is COMPLETELY IGNORANT in the following ways: * It REQUIRES OUTSIDE CODE to do all the work AND to know what and how to do it -- huge mistake. * OUTSIDE CODE can cast Item properties to any other PHP types (booleans, integers, floats, strings, arrays, and objects etc.) -- another huge mistake. Note: we did it correctly above, but what if someone made an array for $price? FYI: PHP has no clue what we mean by an Item, especially by the terms of our class definition above. To PHP, our Item is something with two properties (mutable in every way) and that's it. As far as PHP is concerned, we can pack the entire set of Britannica Encyclopedias into the price slot. When that happens, we no longer have what we expect an Item to be. INSIDE CODE should keep the integrity of the object. For example, our class definition should keep $label a string and $price a float -- which means only strings can come IN and OUT of the class for label, and only floats can come IN and OUT of the class for price. label and $item->price,  *  by using the protected keyword.  * 2. FORCE the use of public functions.  * 3. ONLY strings are allowed IN & OUT of this class for $label  *  via the getLabel and setLabel functions.  * 4. ONLY floats are allowed IN & OUT of this class for $price  *  via the getPrice and setPrice functions.  */ protected $label = 'Unknown Item' ; // Rule 1 - protected. protected $price = 0.0 ;      // Rule 1 - protected. public function getLabel () {    // Rule 2 - public function.  return $this -> label ;       // Rule 3 - string OUT for $label. } public function getPrice () {    // Rule 2 - public function.    return $this -> price ;       // Rule 4 - float OUT for $price. } public function setLabel ( $label )  // Rule 2 - public function. {  /**   * Make sure $label is a PHP string that can be used in a SORTING   * alogorithm, NOT a boolean, number, array, or object that can't   * properly sort -- AND to make sure that the getLabel() function   * ALWAYS returns a genuine PHP string.   *   * Using a RegExp would improve this function, however, the main   * point is the one made above.   */  if( is_string ( $label ))  {   $this -> label = (string) $label ; // Rule 3 - string IN for $label.  } } public function setPrice ( $price )  // Rule 2 - public function. {  /**   * Make sure $price is a PHP float so that it can be used in a   * NUMERICAL CALCULATION. Do not accept boolean, string, array or   * some other object that can't be included in a simple calculation.   * This will ensure that the getPrice() function ALWAYS returns an   * authentic, genuine, full-flavored PHP number and nothing but.   *   * Checking for positive values may improve this function,   * however, the main point is the one made above.   */  if( is_numeric ( $price ))  {   $this -> price = (float) $price ; // Rule 4 - float IN for $price.  } } } ?> Now there is nothing OUTSIDE CODE can do to obscure the INSIDES of an Item. In other words, every instance of Item will always look and behave like any other Item complete with a label and a price, AND you can group them together and they will interact without disruption. Even though there is room for improvement, the basics are there, and PHP will not hassle you... which means you can keep your hair!

If you have problems with overriding private methods in extended classes, read this:)

The manual says that "Private limits visibility only to the class that defines the item". That means extended children classes do not see the private methods of parent class and vice versa also.

As a result, parents and children can have different implementations of the "same" private methods, depending on where you call them (e.g. parent or child class instance). Why? Because private methods are visible only for the class that defines them and the child class does not see the parent's private methods. If the child doesn't see the parent's private methods, the child can't override them. Scopes are different. In other words -- each class has a private set of private variables that no-one else has access to.

A sample demonstrating the percularities of private methods when extending classes:

overridden ();
  }
  private function overridden () {
    echo 'base' ;
  }
}

class child extends base {
  private function overridden () {
    echo 'child' ;
  }
}

$test = new child ();
$test -> inherited ();
?>

Output will be "base".

If you want the inherited methods to use overridden functionality in extended classes but public sounds too loose, use protected. That's what it is for:)

A sample that works as intended:

overridden ();
  }
  protected function overridden () {
    echo 'base' ;
  }
}

class child extends base {
  protected function overridden () {
    echo 'child' ;
  }
}

$test = new child ();
$test -> inherited ();
?>
Output will be "child".

Just a quick note that it's possible to declare visibility for multiple properties at the same time, by separating them by commas. eg:

A class A static public function can access to class A private function : foo ();  } } $a = new A (); A :: bar ( $a ); ?> It's working.

private , $this -> public \n" ;    } } class B extends A {    function __construct ()    {        $this -> private = 2 ;        $this -> public = 2 ;    }    function set ()    {        $this -> private = 3 ;        $this -> public = 3 ;    }    function get ()    {        return parent :: get () . "B: $this -> private , $this -> public \n" ;    } } $B = new B ; echo $B -> get (); echo $B -> set (); echo $B -> get (); ?> ?> Result is A: 1 , 2 B: 2 , 2 A: 1 , 3 B: 3 , 3 This is correct code and does not warn you to use any private. "$this->private" is only in A private. If you write it in class B it's a runtime declaration of the public variable "$this->private", and PHP doesn't even warn you that you create a variable in a class without declaration, because this is normal behavior.

Beware: Visibility works on a per-class-base and does not prevent instances of the same class accessing each others properties! bar , "\n" ;  }  public function setBar ( $value )  {    // Neccessary method, for $bar is invisible outside the class    $this -> bar = $value ;  }    public function setForeignBar ( Foo $object , $value )  {    // this does NOT violate visibility!    $object -> bar = $value ;  } } $a = new Foo (); $b = new Foo (); $a -> setBar ( 1 ); $b -> setBar ( 2 ); $a -> debugBar ( $b );    // 2 $b -> debugBar ( $a );    // 1 $a -> setForeignBar ( $b , 3 ); $b -> setForeignBar ( $a , 4 ); $a -> debugBar ( $b );    // 3 $b -> debugBar ( $a );    // 4 ?>

Please note that protected methods are also available from sibling classes as long as the method is declared in the common parent. This may also be an abstract method. In the below example Bar knows about the existence of _test() in Foo because they inherited this method from the same parent. It does not matter that it was abstract in the parent. _test ();  } } class Foo extends Base {  protected function _test () {    echo 'Foo' ;  } } $bar = new Bar (); $bar -> TestFoo (); // result: Foo ?>

Some Method Overriding rules : 1. In the overriding, the method names and arguments (arg’s) must be same. Example: class p { public function getName(){} } class c extends P{ public function getName(){} } 2. final methods can’t be overridden. 3. private methods never participate in the in the overriding because these methods are not visible in the child classes. Example: class a { private function my(){    print "parent:my"; } public function getmy(){ $this->my(); } } class b extends a{  private function my(){    print "base:my";    } } $x = new b(); $x->getmy(); // parent:my 4. While overriding decreasing access specifier is not allowed class a { public function my(){    print "parent:my"; } } class b extends a{  private function my(){    print "base:my";    } } //Fatal error: Access level to b::my() must be public (as in class a)

1 . If the class member declared as public then it can be accessed everywhere. 2 . If the class members declared as protected then it can be accessed only within the class itself and by inheriting and parent classes. 3 .If the class members declared as private then it may only be accessed by the class that defines the member. tag_line . "" ;  } } // SubClass class child extends pub {  function show (){    echo $this -> tag_line ;  } }  // Object Declaration $obj = new child ; // A Computer Science Portal for Geeks! echo $obj -> tag_line . "" ;  // A Computer Science Portal for Geeks! $obj -> display ();  // A Computer Science Portal for Geeks! $obj -> show (); ?> x - $this -> y . "" ;  }   }  // SubClass - Inherited Class class child extends pro {  function mul () //Multiply Function  {    echo $sub = $this -> x * $this -> y ;  } }  $obj = new child ; $obj -> sub (); $obj -> mul (); ?> name ;  } }  // Object Declaration $obj = new child ; // Uncaught Error: Call to private method demo::show() $obj -> show ();  //Undefined property: child::$name $obj -> display (); ?>

The code prints
test Object ( [public] => Public var [protected:protected] => protected var [private:test:private] => Private var )

Functions like print_r(), var_dump() and var_export() prints public, protected and private variables, but not the static variables.

This has already been noted here, but there was no clear example. Methods defined in a parent class can NOT access private methods defined in a class which inherits from them. They can access protected, though. Example: $method ();  }  } class ChildClass extends ParentClass {  private function privateMethod () {    echo "hi, i'm private" ;  }    protected function protectedMethod () {    echo "hi, i'm protected" ;  }  } $object = new ChildCla
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