Section 12 - Automatic loading of classes_PHP tutorial-PHP Tutorial-php.cn

Section 12 - Automatic loading of classes_PHP tutorial

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Release： 2016-07-21 16:01:12

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| = This article is read by Haohappy<>
| = Notes from the Chapter Classes and Objects
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Section 12 - Automatic loading of classes

When you try to use an undefined class, PHP will report a fatal error. The solution is to add a Class, you can use include to include a file. After all, you know which class you want to use. However, PHP provides the automatic loading function of classes, which can save programming time. When you try to use a class that PHP has not organized, it will Looks for a global function __autoload. If this function exists, PHP will call it with a parameter, which is the name of the class.

Example 6.15 illustrates how __autoload is used. It assumes that the current directory Each file corresponds to a class. When the script attempts to generate an instance of class User, PHP will execute __autoload. The script assumes that the User class is defined in class_User.php. Regardless of whether the call is uppercase or lowercase, PHP will return the lowercase name .

Listing 6.15 Class autoloading

Copy code The code is as follows:

 //define autoload function 
 function __autoload($class) 
 { 
 include("class_" . ucfirst($class) . ".php"); 
 } 

 / /use a class that must be autoloaded 
 $u = new User; 
 $u->name = "Leon"; 
 $u->printName(); 
?> 