Constructors and Destructors

Constructor

void __construct ( [mixed args [, ...]] )
PHP 5 allows developers to declare constructor methods for classes. Classes which have a constructor method call this method on each newly-created object, so it is suitable for any initialization that the object may need before it is used.
Note: Parent constructors are not called implicitly if the child class defines a constructor. In order to run a parent constructor, a call to parent::__construct() within the child constructor is required.

Example :using new unified constructors

class BaseClass {
function __construct() {
print "In BaseClass constructor\n";
}
}

class SubClass extends BaseClass {
function __construct() {
parent::__construct();
print "In SubClass constructor\n";
}
}

$obj = new BaseClass();
$obj = new SubClass();
?>


For backwards compatibility, if PHP 5 cannot find a __construct() function for a given class, it will search for the old-style constructor function, by the name of the class. Effectively, it means that the only case that would have compatibility issues is if the class had a method named __construct() which was used for different semantics.

Destructor

void __destruct ( void )
PHP 5 introduces a destructor concept similar to that of other object-oriented languages, such as C++. The destructor method will be called as soon as all references to a particular object are removed or when the object is explicitly destroyed.

Example : Destructor Example

class MyDestructableClass {
function __construct() {
print "In constructor\n";
$this->name = "MyDestructableClass";
}

function __destruct() {
print "Destroying " . $this->name . "\n";
}
}

$obj = new MyDestructableClass();
?>


Like constructors, parent destructors will not be called implicitly by the engine. In order to run a parent destructor, one would have to explicitly call parent::__destruct() in the destructor body.

Note: Destructor is called during the script shutdown so headers are always already sent.

Note: Attempting to throw an exception from a destructor causes a fatal error.