tailieunhanh - PHP5 Power Programming P2

The old object model not only led to the afore-mentioned problems, but also to fundamental problems that prevented implementing some additional features on top of the existing object model. In PHP 5, the infrastructure of the object model was rewritten to work with object handles. Unless you explicitly clone an object by using the clone keyword, you never create behind-the-scenes duplicates of your objects. In PHP 5, you don’t need a need to pass objects by reference or assign them by reference | Gutmans_Ch01 Page 3 Thursday September 23 2004 2 35 PM Language Features 3 The old object model not only led to the afore-mentioned problems but also to fundamental problems that prevented implementing some additional features on top of the existing object model. In PHP 5 the infrastructure of the object model was rewritten to work with object handles. Unless you explicitly clone an object by using the clone keyword you never create behind-the-scenes duplicates of your objects. In PHP 5 you don t need a need to pass objects by reference or assign them by reference. Note Passing by reference and assigning by reference are still supported in case you want to actually change a variable s content whether object or other type . 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 protected access modifiers for methods and properties. Allows the use of common OO access modifiers to control access to methods and properties class MyClass private id 18 public function getId return this- id Unified constructor name__constructs . Instead of the constructor being the name of the class it is now declared asconstructs which makes it easier to shift classes inside class hier- archies class MyClass function __constructs 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 Gutmans_Ch01 Page 4 Thursday September 23 2004 2 35 PM 4 What Is New in PHP 5 Chap. 1 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 .