Preliminary study on PHP5 (i) _php

Although PHP5 has not yet been officially released (the development version already provides the download), we can now begin to experience the surprises that the new version will bring to us. In the following introduction, we will focus on the three features of PHP5. These three major features are:

* New Object mode
* Exception Handling (Exceptions)
* Namespace (Namespace)

Before you begin, declare two points:

* Examples in the article to illustrate how to operate, some use PHP4 's expressive means, which is only to improve the readability of the article.
* The section described in the article may have some discrepancy with the final release version of PHP5

Before PHP5 is officially released, you can always download from http://snaps.php.net to the latest compiled version to experience the new features PHP5 brings to us in person.

The new object pattern

The objects in the PHP5 have been systematically and comprehensively tuned, and now may look somewhat like Java. This section focuses on the new object patterns in PHP5, with some simpler examples to illustrate. Let this section be a new starting point for your PHP5 journey. ：）

* Constructors and destructors
* References to Objects
* Cloning of objects
* Private, public, and protected modes in the object
* Interface (Interfaces)
* Abstract class
* __call
* __set and __get
* Static members

Constructors and destructors

In PHP4, when a function has the same name as an object, the function becomes the constructor for that object, and there is no concept of destructors in PHP4.
In PHP5, the constructors are uniformly named __construct, and the concept of destructors is introduced, and is uniformly named __destruct.

Example one: constructors and destructors

class Foo {
var $x;
function __construct ($x) {
$this->x = $x;
}
function display () {
Print ($this->x);
}
function __destruct () {
Print ("Bye Bye");
}
}
$o 1 = new Foo (4);
$o 1->display ();
?>

In the example above, when you terminate the call to the Foo class, its destructor will be called, and the above example will output "Bye Bye".

References to Objects

It is well known that in PHP4, passing a variable to a function or method actually makes a copy of the variable, which means that you pass a copy of the variable to the function or method, unless you use the reference symbol "&" to declare that you want to make a reference, not a copy. In PHP5, objects always exist in the form of references, and the assignment operation in an object is also a reference operation.

Example two: reference to an object

class Foo {
var $x;
function SetX ($x) {
$this->x = $x;
}
function GetX () {
return $this->x;
}
}
$o 1 = new Foo;
$o 1->setx (4);
$o 2 = $o 1;
$o 1->setx (5);
if ($o 1->getx () = = $o 2->getx ()) print ("Oh my god!");
?>

Cloning of Objects

As mentioned above, when an object is always invoked as a reference, what if I want to get a copy of the object? PHP5 provides a new function, that is, the cloning of objects, the syntax is __clone.

Example three: Cloning of an object
class Foo {
var $x;
function SetX ($x) {
$this->x = $x;
}
function GetX () {
return $this->x;
}
}
$o 1 = new Foo;
$o 1->setx (4);
$o 2 = $o 1->__clone ();
$o 1->setx (5); if ($o 1->getx ()! = $o 2->getx ()) print ("Copies is Independant");
?>

The method of object cloning exists in many other application languages, so you don't have to worry about its stability. ：）

Private, public, and protected modes in an object

In PHP4, all methods and variables of an object are public, which means that you can manipulate any one of the variables and methods in the outer part of an object. PHP5 introduces three new modes for controlling this access, which are public, protected (Protected), and private (privately).

Common mode (public): Allows manipulation control outside the object.
Private mode: Only the methods within this object are allowed to manipulate it.
Protected Mode (Protected): Allows this object and its parent object to manipulate it.

in the object,!--? PHP class Foo {
private $x;
Public Function Public_foo () { br> print ("I ' m public");
}
Protected function Protected_foo () {
$this->private_foo ();//ok because we is in the same class we can Call Private methods
Print ("I ' m protected");
}
Private Function Private_foo () {
$this->x = 3;
Print ("I ' m Private");
}
}
Class Foo2 extends Foo {
Public function display () {
$this->protected_foo ();
$this->public_fo O ();
//$this->private_foo ();//invalid! The function is private in the base class
}
} $x = new Foo ();
$x->public_foo ();
//$x->protected_foo ();//invalid cannot call protected methods outside the class and derived classes
//$x->p Rivate_foo (); Invalid private methods can only be used inside the class $x 2 = new Foo2 ();
$x 2->display ();
?

Tip: Variables in objects are always private, and it is not a good object-oriented programming habit to manipulate variables directly in an object, and a better way to do this is to hand over the variables you want to an object.

Interface (Interfaces)

As we all know, objects in PHP4 support inheritance, and to make an object a derived class of another object, you need to use code like "class Foo extends parent" to control it. In PHP4 and PHP5, an object can inherit only once, and multiple inheritance is not supported. However, there is a new noun in PHP5: interface, interface is a special object that has no specific processing code, it just defines the name and parameters of some methods, then the object can easily use the ' implement ' keyword to integrate the required interface, and then add the specific execution code.

Example five: interface

Interface Displayable {
function display ();
}
interface Printable {
function Doprint ();
}

Class Foo implements displayable,printable {
function display () {
Code
} function Doprint () {
Code
}
}
?>

This is to improve the readability of the code and the popularity of a great help, through the above example can be seen, the object Foo contains the displayable and printable two interfaces, then we can clearly know that the object Foo will have a display () method and a print () method, you can easily manipulate the object without worrying about how the object's interior works, just to understand the interface part.

To be Continued ~ ~

