New Object-Oriented Features

The new OO features are too numerous to give a detailed description in this section. Chapter 3, “PHP 5 OO Language,” details each feature.The following list provides the main new features:

public/private/protectedaccess modifiers for methods and properties.Allows the use of common OO access modifiers to control access tomethods and properties:




class MyClass {
private $id = 18;
public function getId() {
return $this->id;
}
}


Unified constructor name__construct().
Instead of the constructor being the name of the class, it is now declared as __construct(), which makes it easier to shift classes inside class hierarchies:


class MyClass {
function __construct() {
print "Inside constructor";
}
}

Object destructor support by defining a __destructor() method.Allows defining a destructor function that runs when an object is destroyed:




class MyClass {
function __destruct() {
print ”Destroying object”;
}

}

Interfaces.

Gives the ability for a class to fulfill more than one is-a relationships. A class can inherit only from one class, but may implement as many interfaces as it wants:


interface Display {
function display();
}
class Circle implements Display {
function display() {
print "Displaying circle\n";
}
}




instance of operator.


Language-level support for is-a relationship checking. The PHP 4 is_a() function is now deprecated:




if ($obj instanceof Circle) {
print '$obj is a Circle';
}


Final methods.

The final keyword allows you to mark methods so that an inheriting class cannot overload them:


class MyClass {
final function getBaseClassName() {
return __CLASS__;
}
}


Final classes.

After declaring a class as final , it cannot be inherited. The following example would error out.


final class FinalClass {
}
class BogusClass extends FinalClass {
}


Explicit object cloning.

To clone an object, you must use the clone keyword. You may declare a __clone() method, which will be called during the clone process (after the properties have been copied from the original object):