Home > Common Problem > body text

What is the difference between define and define

清浅
Release: 2020-09-08 09:08:28
Original
7691 people have browsed it

The differences between define and defined are: 1. Define is used to define a constant and it cannot be changed or canceled after it is defined; 2. Define checks whether the constant is defined and returns true if it exists. Returns false if it does not exist.

What is the difference between define and define

[Recommended tutorial: PHP tutorial]

define and defined The difference

define

define is used to define a constant. The constant represents the global scope, so it can be used directly in the script without considering the scope. accessible from anywhere. But one thing to note is that once a constant is defined, it cannot be changed or undefined

Example:

define("path","root/www/web")
Copy after login

where root/www/web is the value of the constant

defined

#defined is used to detect whether the constant is defined. If the constant exists, it returns true. If it does not exist, it returns false.

Example :

defined('APP_PATH') or define('APP_PATH', dirname($_SERVER['SCRIPT_FILENAME']) . DS);
Copy after login

The meaning of the above code is that if app_path is defined, it will return true. If it is not defined, it will execute the code after or

Summary: The above is the entire content of this article. I hope to be helpful

The above is the detailed content of What is the difference between define and define. For more information, please follow other related articles on the PHP Chinese website!

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
Latest Articles by Author
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template
About us Disclaimer Sitemap
php.cn:Public welfare online PHP training,Help PHP learners grow quickly!