v 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";

}

}

v Instanceof  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';

}

v 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__;

}

}

v 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

{

}

v 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):