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PHP 5 Tutorials – Static Data Members and Methods Posted: 12 Feb 2008 01:47 AM PST In this tutorial you will learn all about static data members and methods Meaning of static data members Meaning of static methods Defining static data members in PHP5 Defining static methods in PHP5 Accessing static data members in PHP5 Accessing static methods in PHP5 Rules to keep in mind for static methods Meaning of static data members A data member that is commonly available to all objects of a class is called a static member. Unlike regular data members, static members share the memory space between all objects of the same class. Meaning of static methods A static method is a class method that can be called without creating an instance of a class. Such methods are useful when creating utility classes. Defining static data members in PHP5 To define a static member in PHP5 you need to prefix the class member name with the keyword ‘static’. Look at the example below.   class Customer {   private $first_name; // regular member static public $instance_count; //static data member   } In the above example $instance_count is declared as a static data member Defining static methods in PHP5 To define a static data methods in PHP5 you need to prefix the class method name with the keyword ‘static’. Look at the example below.   class Customer {   public function getFirstName() { //body of method }   static public function getInstanceCount() { //body of method } } In the above example getInstanceCount is declared as a static method Accessing static data members in PHP5 A static member data can be accessed using the name of the class along with the scope resolution operator (::) i.e. you don’t need to create an instance of that class Look at the example below:   class Customer {   static public $instance_count = 0; //static data member   public function __construct() { Customer::$instance_count++; }   public function __destruct() { Customer::$instance_count--; }   public function getFirstName() { //body of method }   static public function getInstanceCount() { //body of method } }   $c1 = new Customer(); $c2 = new Customer();   echo Customer::$instance_count; Output: 2 In the above example, $instance_count is a static data member. Every time a new object is created the constructor is executed and the $instance_count variable is incremented by one. To echo the value contained in $instance_count variable, we use the :: (scope resolution) operator. Accessing static method in PHP5 A static method can be accessed using the name of the class along with the scope resolution operator (::) i.e. you don’t need to create an instance of that class. However, you can also access it with an instance variable. Look at the example below:   class Customer {   static public $instance_count = 0; //static data member   public function __construct() { Customer::$instance_count++; }   public function __destruct() { Customer::$instance_count--; }   public function getFirstName() { //body of method }   static public function getInstanceCount() { return Customer::$instance_count; } }   $c1 = new Customer(); $c2 = new Customer();   echo Customer::getInstanceCount(); //this is using the scope resolution operator echo $c1->getInstanceCount(); //this is using the instance variable Output: 2 2 Rules to keep in mind for static methods A static method can only access static data members A static method does not have access to the $this variable Please feel free to write back for any clarification. Subscribe to my newsletter: Related Posts on PHP5 Tutorial – Object Oriented Programming (OOPS) PHP5 Tutorial – Learn to create a PHP5 Class PHP5 Tutorial – Learn to Create a PHP5 Class Object PHP5 Tutorial – Defining Attributes of a PHP5 Class PHP5 Tutorial – Defining Methods of a PHP5 Class PHP5 Tutorial – Creating a PHP5 Constructor __construct() PHP5 Tutorial OOPS – Creating a PHP5 Destructor __destruct() PHP5 Tutorial OOPS – PHP5 Class Access Specifiers – public, private and protected PHP5 Tutorial – $this variable explained PHP5 Tutorial – instanceOf Operator Explained PHP5 Tutorial – Defining Class Constants PHP5 Tutorial – Inheritance PHP5 Tutorials – Abstract Class and Interface PHP5 OOPS Tutorials – Polymorphism PHP5 Tutorial – Magic Methods – __toString() method PHP5 Tutorial – Magic Methods – __get() and __set() PHP5 Tutorial – Magic Methods – __isset() and __unset() PHP5 Tutorial – Magic Methods – __call() method PHP5 Tutorial – Magic Methods – __autoload() method PHP5 Tutorial – Magic Methods – __sleep() and __wakeup() PHP5 Tutorial – Magic Methods – __clone() method

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