如何在许多其他页面已经包含的文件中包含php文件PHP

Question

Can it be possible to include a PHP file into another file which is already included in many other files on different paths

For example I have the following files and directories:

domain/include/header.php
domain/include/body.php
domain/include/user_data.php

header.php file contains user_data.php and header.php file itself contained in many other pages on different location:

domain/index.php
domain/home/index.php
domain/home/user/index.php

I want to access my user_data.php file within one( ie header.php ) and don't want to include it again and again in each file.

How is this possible?

Answer 1

参见include_once和require_once

Answer 2

Yeah why not. You can create master include file and that file includes all other files from the directory.

So your header.php file will look something like this,

<?php
    include('user_data.php'); // Assuming file is in same location.

Now include only header.php file where every you want, it will automatically includes user_data.php along with it.

Extra:

This is useful for including database connection files.

You can also use this file include root level JS and CSS so you don't have include those assets on every page.

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Using include_once() is good practice, as if you have included user_data.php file somewhere in other files and it also gets include from the hedaer.php file, It won't get included twice.

As that is all include_once() does, it includes the file content only once per execution.

The only difference between include() and include_once() that if the code from a file has already been included, it will not be included again, and include_once returns TRUE .