What does require mean in php

The function of the require function in PHP is to include another PHP file and insert the contents of the file into the current script. Its steps include: checking whether the file exists, checking readability, and including the file. require is suitable for including function libraries, HTML code, or configuration settings, but excessive use can cause performance issues.

The meaning of Require in PHP

require is a function in PHP, used Just include another PHP file in the script. It inserts the contents of the specified file into the current script, as if the file had been copy-pasted into that location.

Principle of action

When the require function is called, it will perform the following steps:

1. Check whether the file exists: It will check whether the specified PHP file exists.
2. Check if the file is readable: It will ensure that the current script has permission to read the file.
3. Include files: If the file exists and is readable, require will insert the contents of the file into the current script.

Advantages and Disadvantages

Advantages:

• Allows modular code organization, making large projects Easier to manage.
• The code can be simplified when the same file needs to be included multiple times.

Disadvantages:

• If the included file does not exist or is unreadable, a fatal error will occur, causing the entire script to fail to execute.
• Including too many files may cause performance issues because PHP will parse and execute the file every time require is called.

Usage scenarios

require Usually used in the following situations:

• Contains public function libraries or Class definition.
• Contains the HTML code for a specific form or page.
• Introduce configuration settings or constants defined in other scripts.

Example

<code class="php"><?php
// 引入一个包含函数的 PHP 文件
require 'functions.php';

// 现在可以在当前脚本中使用这些函数
echo calculate_area(10, 15);
?></code>

Note:

require and include Functions are similar, but slightly different. include only produces a warning if the file does not exist or is unreadable, whereas require produces a fatal error.

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