When using the ThinkPHP framework, viewing its source code is useful for the two functions __autoload and apl_autoload_register, and these two functions are used for automatic loading. Its main function is that when your source code file uses a file that has not been loaded, these two functions will be triggered to load the unloaded file.
php's __autoload function is a magic function. Before this function appeared, if 100 objects were referenced in a PHP file, then the file would need to use include or require to introduce 100 class files, which would cause the PHP file to be extremely large. So there is this __autoload function.
When is the __autoload function called?
When the new keyword is used in the PHP file to instantiate an object, if the class is not defined in the PHP file, the __autoload function will be triggered. At this time, the definition of the class can be introduced. php file, and then it can be instantiated successfully. (Note: If the object that needs to be instantiated has been found in this file and the definition of the class has been found, the __autoload function will not be triggered)
#Animal.php<?php class Animal{}?>
#main.php<?php function __autoload($classname){ $classpath = "{$classname}.php"; if(file_exists($classpath)){ require_once($classpath); }else{ echo $classpath." not be found!"; } } $ani = new Animal();?>
Like the above two files, run php main.php
(1) When running to new Animal(), it is found that class Animal is not defined;
(2) The __autoload function is triggered, which introduces the Animal.php file;
(3) The instantiation is successful.
Okay, after understanding the role of the __autoload function, let’s take a look at the role of the spl_autoload_register function.
The role of the spl_autoload_register function is to replace the custom function settings with the __autoload function (note: when __autoload and spl_autoload_register appear in the file at the same time, spl_autoload_register shall prevail)
Then changing main.php to the following will have the same effect Function:
#main.php<?php function myLoad($classname){ $classpath = "{$classname}.php"; if(file_exists($classpath)){ require_once($classpath); }else{ echo $classpath." not be found!"; } } spl_autoload_register("myLoad"); $ani = new Animal();?>
When using the ThinkPHP framework, it is useful to check its source code to use the two functions __autoload and apl_autoload_register, and these two functions are used for automatic loading. Data source https://blog.csdn.net/gavin_new/article/details/52805811
Its main function is that when your source code file uses a file that has not been loaded, these two functions will be triggered to load it. This unloaded file
php's __autoload function is a magic function. Before this function appears, if a php file references 100 objects, then this file needs to use include or require to introduce 100 objects. class file, which will cause the php file to be extremely large. So there is this __autoload function.
When is the __autoload function called?
When the new keyword is used in the PHP file to instantiate an object, if the class is not defined in the PHP file, the __autoload function will be triggered. At this time, the definition of the class can be introduced. php file, and then it can be instantiated successfully. (Note: If the object that needs to be instantiated has been found in this file and the definition of the class has been found, the __autoload function will not be triggered)
#Animal.php<?php class Animal{}?>
#main.php<?php function __autoload($classname){ $classpath = "{$classname}.php"; if(file_exists($classpath)){ require_once($classpath); }else{ echo $classpath." not be found!"; } } $ani = new Animal();?>
Like the above two files, run php main.php
(1) When running to new Animal(), it is found that class Animal is not defined;
(2) The __autoload function is triggered, which introduces the Animal.php file;
(3) The instantiation is successful.
Okay, after understanding the role of the __autoload function, let’s take a look at the role of the spl_autoload_register function.
The role of the spl_autoload_register function is to replace the custom function settings with the __autoload function (note: when __autoload and spl_autoload_register appear in the file at the same time, spl_autoload_register shall prevail)
Then changing main.php to the following will have the same effect Role:
#main.php<?php function myLoad($classname){ $classpath = "{$classname}.php"; if(file_exists($classpath)){ require_once($classpath); }else{ echo $classpath." not be found!"; } } spl_autoload_register("myLoad"); $ani = new Animal();?>
The above is the detailed content of Detailed explanation of two PHP automatic loading functions. For more information, please follow other related articles on the PHP Chinese website!

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

Dreamweaver Mac version
Visual web development tools

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software