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In my previous PHP5 OOPS tutorial on PHP5 Tutorial – Magic Methods – __get() and __set(), we learnt how and when to use these magic methods.

This PHP5 OOPS tutorial will teach you how and when to use the magic methods __isset() and __unset().

These methods are automatically called internally when isset() and unset() is called on undeclared data members. The magic method __isset() method receives an argument – the value of which is the name of the variable that the program wants to test if the variable is set or not.

The magic method __unset() method receives an argument – the value of which is the name of the variable that the program wants to unset.

Look at the example below:

class Customer {
	private $data = array();
 
	public function __set($dt, $vl) {
		$this->data[$dt] = $vl;
	}
 
	public function __get($dt) {
		return $this->data[$dt];
	}
 
	public function __isset($dt) {
		return isset($this->data[$dt]);
	}
 
	public function __unset($dt) {
		return unset($this->data[$dt]);
	}
}
 
$c = new Customer();
$c->name = "Sunil Bhatia";
 
echo isset($c->name)."\n";
echo unset($c->name);

In the example above the script creates a new Customer Object. The program assigns a string value to an undeclared variable i.e. $c->name. The undeclared variable is handled by the magic method __set(). Read this post on PHP5 Magic Methods __set() if you need more understanding how the magic method __set() works.

The program ties to check if the undeclared variable i.e., $c->name has been set or not using the PHP method isset(). Since $c->name is an undeclared variable the PHP5 magic method __isset() is invoked that takes the name of the undeclared variable i.e. “name” and checks if the internal array $data["name"] is set or not.

Similarly, when the program calls unset() on the undeclared variable i.e. $c->name, the PHP5 magic method __unset() is invoked that takes the name of the undeclared variable i.e. “name” and unsets the internal array $data["name"].

Related Posts on PHP5 Tutorial – Object Oriented Programming (OOPS)

1. PHP5 Tutorial – Learn to create a PHP5 Class
2. PHP5 Tutorial – Learn to Create a PHP5 Class Object
3. PHP5 Tutorial – Defining Attributes of a PHP5 Class
4. PHP5 Tutorial – Defining Methods of a PHP5 Class
5. PHP5 Tutorial – Creating a PHP5 Constructor __construct()
6. PHP5 Tutorial OOPS – Creating a PHP5 Destructor __destruct()
7. PHP5 Tutorial OOPS – PHP5 Class Access Specifiers – public, private and protected
8. PHP5 Tutorial – Magic Methods – __toString() method
9. PHP5 Tutorial – Magic Methods – __get() and __set()
10. PHP5 Tutorial – Magic Methods – __isset() and __unset()
11. PHP5 Tutorial – Magic Methods – __call() method
12. PHP5 Tutorial – Magic Methods – __autoload() method
13. PHP5 Tutorial – Magic Methods – __sleep() and __wakeup()
14. PHP5 Tutorial – Magic Methods – __clone() method