Php Protected Private
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Php Protected Private
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Keywords are basically a set of special words that are reserved in every programming language for a specific purpose. They can be either commands or parameters and they cannot be used for common use like variable names. Protected in PHP are predefined in all languages including PHP and also called reserved names.
There are 5 kinds of access modifiers in PHP:
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We shall concentrate on only protected access modifiers in this article. Apart from variables, protected keywords are also used for declaring methods/functions and properties as protected. Unless specified explicitly, all the variables and methods will be public by default. The protected variable decreases the visibility of the respective variable or method because its access is restricted to the class in which it is declared. Protected access modifiers cannot be applied for classes.
However, they can be called by a subclass which is inherited from its parent class. Hence one can declare the required method or a variable as protected by prefixing it with a “protected” keyword.
Here we can see that using protected keyword we are declaring both variable and function names.
Working of protected modifiers in PHP: Like the private access modifier, we can also use protected for restricting the usage and accessing of class functions and variables outside of the class. But one exception of protected from private variables is that they can be accessed through inheritance from its parent class in a subclass.
Let us understand the usage and working of protected modifier in detail by taking a simple example below:
After commenting on line 29 which is trying to call the protected method
In the above example, we are showcasing the different mathematical operations like addition, division, and multiplication. First, we are declaring division() function without any access modifier. Hence by default, it is public and the division value we are performing on both variables a and b are displayed in the output when we call the function by creating its object. But when we try to call the protected function multiply() we get the error inline 34 saying that protected method cannot be called.
Whereas we can call and get the value of a protected method via inheritance as shown. Here the child class and is inherited from parent class Math and hence we are able to call the protected variables a and b without any error.
In this example, we are first declaring the main parent class Animal and initializing a protected variable as $animal which is an array containing names of 3 different animals. Next, we are also declaring a protected function in which we are giving a unique description to each of the animals in the array.
Since protected variables can be accessed using subclass, we are here creating another subclass Dog from the parent class Animal. Also to showcase that public functions can be accessed anywhere, we declare a public function to output variable dog’s description.
Next, we create an object of both classes Animal and Dog and try to access their variables which are protected. Hence for lines 40, 41 and 42, we get a fatal error telling that protected properties/methods/variables cannot be accessed. Hence we cannot access any variables outside of class Animal since all are protected.
Hence protected variables are those access modifiers that are used for controlling specifically defined variables or methods or properties in a class. It needs to be explicitly specified by prefixing and hence can be accessed only within its declared package and by a subclass that inherits from the parent package.
This is a guide to Protected in PHP. Here we discuss the Introduction, Example of a Protected Variable and Method and Importance of Protected in PHP. You can also go through our other suggested articles to learn more–
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What is the difference between public, private, and protected in PHP?
Difficulty Level :
Hard Last Updated :
06 Oct, 2021
public $tag_line = "A Computer Science Portal for Geeks!" ;
echo $this ->tag_line. "" ;
// A Computer Science Portal for Geeks!
// A Computer Science Portal for Geeks!
// A Computer Science Portal for Geeks!
echo $sum = $this ->x- $this ->y . "" ;
function mul() //Multiply Function
echo $sub = $this ->x* $this ->y;
private $name = "A Computer Science Portal for Geeks!" ;
echo "This is private method of base class" ;
// Uncaught Error: Call to private method demo::show()
protected $protected = 'Protected' ;
private $private = 'Private' ;
echo $this -> protected ;
echo $obj -> protected ; // Cannot access protected property
echo $obj -> private ; // Cannot access private property
$obj ->Display(); //Displays all properties
public $public = 'Public Sub Class' ;
protected $protected = 'Protected Sub Class' ;
echo $this -> protected ;
echo $obj2 -> protected ; // Cannot access protected property
echo $obj2 -> private ; // Cannot access private property
$obj2 ->Display(); //Displays all properties
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Got It !
Public, private and protected are called access modifiers. Just like C++, PHP also have three access modifiers such as public, private and protected. The visibility of a property, a method or a constant can be defined by prefixing the declaration with these keywords.
Public Access modifier: This modifier is open to use inside as well as outside the class. Example:
Protected Access modifier: This modifier is open to use within the class in which it is defined and its parent or inherited classes. Example:
Private Access modifier: This modifier is open to use within the class that defines it. ( it can’t be accessed outside the class means in inherited class). Example:
Miscellaneous example: Example:
PHP is a server-side scripting language designed specifically for web development. You can learn PHP from the ground up by following this PHP Tutorial and PHP Examples .
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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 ();
}
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