Home > Backend Development > PHP Tutorial > PHP automatic loading class __autoload() function_PHP tutorial

PHP automatic loading class __autoload() function_PHP tutorial

WBOY
Release: 2016-07-13 10:13:28
Original
732 people have browsed it

php automatically loads classes __autoload() function

When many developers write object-oriented applications, they create a PHP source file for the definition of each class. A big annoyance is having to write a long list of include files at the beginning of each script (one file per class).

In a software development system, it is impossible to write all classes in a PHP file. When a class declared in another file needs to be called in a PHP file, the file needs to be introduced through include. However, sometimes, in projects with many files, it is a headache to include all the files of the required classes one by one. So, can we include this class when it is used? Where to import the php file? This is what we are going to talk about here Auto-loading class.

In PHP 5, you can define an __autoload() function, which will be automatically called when trying to use a class that has not yet been defined. By calling this function, the script engine has the last chance to load what is needed before PHP fails with an error. class, one parameter received by the __autoload() function is the class name of the class you want to load, so when you are working on a project, you need to follow certain rules when organizing the file names of the defined classes. It is best to center on the class name. , you can also add a unified prefix or suffix to form the file name, such as xxx_classname.php, classname_xxx.php and classname.php, etc.

This example attempts to load the MyClass1 and MyClass2 classes from the MyClass1.php and MyClass2.php files respectively

<?php
function __autoload($classname)
{
	require_once $classname . '.php';
}

//MyClass1类不存在时,自动调用__autoload()函数,传入参数”MyClass1”
$obj = new MyClass1();

//MyClass2类不存在时,自动调用__autoload()函数,传入参数”MyClass2”
$obj2 = new MyClass2();
?>
Copy after login

The processing method of DiscuzX2.5 is:

<?php
if (function_exists('spl_autoload_register'))
{
	spl_autoload_register(array('core', 'autoload'));
}
else
{
	function __autoload($class)
	{
		return core::autoload($class);
	}
}
Copy after login


Note: __autoload() is specially designed for classes that do not exist! ! ! Many frameworks use this function to implement automatic loading of class files ! ! !

Articles you may be interested in

  • How to set up phpmyadmin to automatically log in and cancel automatic login
  • PHP function to check browser parameters to prevent SQL injection
  • Detailed explanation of how to use the jQuery plug-in (Lazy Load) for delayed loading of images
  • Some forgotten powerful string processing functions in php
  • How to implement automatic login next time by remembering the password in php
  • Solution to the invalid automatic verification and automatic filling of thinkphp
  • PHP function to obtain the complete URL address of the current page, including parameters
  • PHP encryption and decryption function

www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/915939.htmlTechArticlephp automatically loads classes __autoload() function. When many developers write object-oriented applications, each class The definition creates a PHP source file. A big annoyance is having to put it on each foot...
Related labels:
source:php.cn
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template