How to use php require_once

This article mainly explains "how to use php require_once", the explanation content in the article is simple and clear, easy to learn and understand, please follow the idea of Xiaobian slowly in-depth, together to study and learn "how to use php require_once"!

In php, the require_once statement is used to reference or include an external php file with the syntax "require_once(filename)" or "require_once 'filename'"; if the file specified by the statement has already been included, it will not be included again.

Operating environment of this tutorial: Windows 7 system, PHP7.1 version, DELL G3 computer

php require_once statement

require_once: Its role is the same as that of require, both reference or contain an external php file

Principle: When the php file containing require_once is executed, the external file specified by require_once will be included, and other code will form a new php file and start execution.

Syntax: "require_once(filename)" or "require_once 'filename'"

Note:

1. When the external included file has errors, it will also run incorrectly and terminate the operation.

When applying the require_once statement, it will first check whether the file to be included has already been included elsewhere in the program, and if so, it will not be included again.

Examples:

a.php

b.php

The result of running b.php is:

Hello

Note: The result is only a Hello output, indicating that the code in a.php has only been referenced once.

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