PHP5 Tutorial OOPS - PHP5 Class Access Specifiers - public, private and protected
Posted on : 14-11-2007 | By : admin | In : PHP, PHP Tutorials, PHP5 OOPS Tutorials
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In the earlier tutorials we have witnessed keywords like public, private and protected. These are nothing but access specifiers. So, lets understand what access specifiers are.
Definition of Access Specifiers
Access specifiers specify the level of access that the outside world (i.e. other class objects, external functions and global level code) have on the class methods and class data members. Access specifiers can either be public, private or protected.
Why do we need Access specifiers
Access specifiers are used as a key component of Encapsulation and Data Hiding. By using either of the access specifiers mentioned above i.e. public, private or protected you can hide or show the internals of your class to the outside world.
Explanation of each access specifier
1. Private
2. Protected
3. Public
1. Private
A private access specifier is used to hide the data member or member function to the outside world. This means that only the class that defines such data member and member functions have access them. Look at the example below:
class Customer { private $name; public function setName($name) { $this->name = $name; } public function getName() { return $this->name; } } $c = new Customer(); $c->setName("Sunil Bhatia"); echo $c->name; //error, $name cannot be accessed from outside the class //$name can only be accessed from within the class echo $c->getName(); //this works, as the methods of the class have access //to the private data members or methods
In the above example, echo $c->name will give you an error as $name in class Customer has been declared private and hence only be accessed by its member functions internally. Therefore, the following line echo $c->getName() will display the name.
2. Public
A public access specifier provides the least protection to the internal data members and member functions. A public access specifier allows the outside world to access/modify the data members directly unlike the private access specifier. Look at the example below:
class Customer { public $name; public function setName($name) { $this->name = $name; } public function getName() { return $this->name; } } $c = new Customer(); $c->setName("Sunil Bhatia"); echo $c->name; // this will work as it is public. $c->name = "New Name" ; // this does not give an error.
In the above example, echo $c->name will work as it has been declared as public and hence can be accessed by class member functions and the rest of the script.
3. Protected
A protected access specifier is mainly used with inheritance. A data member or member function declared as protected will be accessed by its class and its base class but not from the outside world (i.e. rest of the script). We can also say that a protected data member is public for the class that declares it and it’s child class; but is private for the rest of the program (outside world). Look at the example below:
class Customer { protected $name; public function setName($name) { $this->name = $name; } public function getName() { return $this->name; } } class DiscountCustomer extends Customer { private $discount; public function setData($name, $discount) { $this->name = $name; //this is storing $name to the Customer //class $name variable. This works // as it is a protected variable $this->discount = $discount; } } $dc = new DiscountCustomer(); $dc->setData("Sunil Bhatia",10); echo $dc->name; // this does not work as $name is protected and hence // only available in Customer and DiscountCustomer class
In the above example, echo $dc->name will not work work $name has been defined as a protected variable and hence it is only available in Customer and DiscountCustomer class.
You will learn more about inheritance later in this tutorial series. You should revisit this tutorial and read more on the protected section again when you understand inheritance better.
Important Note of Access Specifier in PHP5
In PHP5, access specifiers are public by default. This means that if you don’t specify an access specifier for a data member or method then the default ‘public’ is applicable.
Feel free to write comments if you need more examples or if you need to ask a question on PHP5 Class. You can also subscribe to my notification service to be informed as an when a new tutorial article goes online. Subscribe Below
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- PHP5 Tutorial OOPS - Creating a PHP5 Destructor __destruct()
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great series of tutorials, i hope you keep them coming,
thank you very much.
This tutorial is helpful to me to understand the concept of access specifiers in php5 but please give some example of their use in web programming.
As I am fresher and new in web development. I am good in oops concepts and want to implement in web development.
Thanks
Regards,
Rajesh Bhatia
Dear sir,
your php 5 OOP tutorial is very helpfull for me.
Now I understand that what is access specifiers and how these access specifiers works.
1. Private
2. Protected
3. Public
Thanks
Regards,
Rahul
Awesome.. Excellent Series.
The examples and explanation provided in each section seems quite friendly. no one has explained me things clearly as you have done..
Thanks Buddy
Conscies preicious and towards goal.
little and powerful explation.
want more from u on each topic of php5.
thanks.
hetalsagar(at)rediffmail(dot)com
I just read your tutorials once and i understood the differences of the PHP OOP access specifiers. Its very good tutorials and well explained. Thank you so much… I look forward to see a small PHP OOP application if possible in the future… God bless you…
This is simplest and the easiest tutorial i have come across which explains in a very basic and understanding language without making it complex. It was really helpful for me.
Thanks Sunil for using simple examples that illustrate the concept without introducing lots of superfluous details. Your style is needed on the PHP documentation, which sometimes uses bizarre examples that do more to confuse than clarify. I especially appreciate your using a simple inheritance example to illustrate the use of protected visibility on class members. Many other sites try to illustrate this concept without inheritance, which doesn’t make much sense.
This is simplest and the easiest tutorial i have come across which explains in a very basic and understanding language without making it complex. It was really helpful for me
your php 5 OOP tutorial is very helpfull for me.
Now I understand that what is access specifiers and how these access specifiers works.
1. Private
2. Protected
3. Public
This tutorial is helpful to me to understand the concept of access specifiers in php5 but please give some example of their use in web programming.
As I am fresher and new in web development. I am good in oops concepts and want to implement in web development.
I just read your tutorials once and i understood the differences of the PHP OOP access specifiers. Its very good tutorials and well explained. Thank you so much… I look forward to see a small PHP OOP application if possible in the future… God bless you…
Thanks Sunil for using simple examples that illustrate the concept without introducing lots of superfluous details. Your style is needed on the PHP documentation, which sometimes uses bizarre examples that do more to confuse than clarify. I especially appreciate your using a simple inheritance example to illustrate the use of protected visibility on class members. Many other sites try to illustrate this concept without inheritance, which doesn’t make much sense.
sir, your series of PHP 5 OOPS is very very usefull for me, many big thanks
Regard
Agus
Sir, what the difenrence if we declere the acces specifiers or not? e.g just write:
$name
or
var $name
rather than
public $name
Thank You
great tutorial , keep posting please !!!!!!!!
your php 5 OOP tutorial is very helpfull for me.
Now I understand that what is access specifiers and how these access specifiers works.
1. Private
2. Protected
3. Public
Sir, what the difenrence if we declere the acces specifiers or not? e.g just write:
$name
or
var $name
rather than
public $name
Thank You
Excellent tutorial. superb explaination. can you please give some more examples for tough concepts? Also i am looking forward a Zend framework tutorial from you since you explain the concepts better. Thank you very much Sunil !
very good tutorials. try to give the more tutorials.
Very nicely explained the difference of public,private and protected data types in PHP.
Thank you verry much , verry helpfull.
Like this i want to be teached .
document are gud which heip me very much but there should be more example for access specifier.
THANKS FOR THE TUTORIAL ITS NICE.
very good tutorials.
Thank You Very Much.
This is a great tutorial for OOP in php. I’m a newbie working with php scripts.
I’ve been studying class inheritance in php and I’d like to see some examples of using global scope resolution to assign values from a base class members to a child class member.
very nice tutorial……but i just want to know is it necessary to specify access specifiers for each and every data members in a class…..hoping for a reply………..thanx..
// Private Property in parent class IS BROKEN DOWN in subclass ?
// We have 2 classes :
class User // Parent class
{
private $name; // This is problem. It’s private
protect $pass; // The second property is protect.
}
// Subclass
class Admin extends User
{
public function in_pass()
{
echo “Name is “.$this->name.”With pass is ” . $this->pass.”";
}
}
// now we run it :
$HLP = new Admin();
$HLP->name = “Linh”; // It should have had error but it still runs normally (because it is private property)
$HLP->pass = “123456″; // But This one is die (of couse, its property is protect.
$HLP->in_pass();
// if we change the property of $pass -> private or public , Program runs very well :O
// My PHP version is 5.3.0.
// Please help me to explain it. Thanks.
Yes, Indeed, VERY HELPFUL! Thanks for sharing your knowledge to everyone. Keep posted such articles!
Great !! Thanks for your helpful article over oops concepts in php .
Good tutorials. Nice work!
Your tutorials are realy helpful to me to understand the concept of oops php5 but please give some example of their use in web programming.
Thanks
Inderji Singh