ZEND PHP 5 Certification STUDY GUIDE

254 ” Differences Between PHP 4 and 5
Objects
• For all intents and purposes, all objects in PHP 5 are passed by reference. This
means that assigning an object to a variable will not create a copy of the former,
but simply creates another reference to it.
• Constants, as well as static methods and properties, can now be defined within
the scope of a class.
• Class methods and properties now feature visibility, and can be declared as
public, private or protected. Classes and methods can also be declared as
final to prevent further inheritance.
• Since all objects are assigned by reference, you now need a specialized mechanism
to copy objects. This is provided by the clone construct and the __clone()
magic method.
• PHP 5 features unified constructors and destructors—all constructors should
now be named __construct(), and the new __destruct() magic method has
been added for object destruction.
• With the addition of interfaces and abstract classes, PHP developers now have
far greater control over how they implement their object-oriented code. Interfaces
can be used to define common APIs, while abstract classes provide
models for class implementations that follow a specific blueprint.
• Class definitions can now be loaded on demand by using the __autoload()
function.
Magic Methods
Licensed to 482634 - Amber Barrow (itsadmin@deakin.edu.au)
A multitude of new “magic” methods has been introduced in PHP 5:
• __get() and __set() are called when accessing or assigning an undefined object
property, while __call() is executed when calling a non-existent method
of a class.