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Scenarios in PHP that use get_include_path() and include_once()

gitbox 2025-05-26

Inclusion and management of files are very common requirements during PHP project development. Rationally managing inclusion paths can not only improve the maintainability of the code, but also avoid problems caused by duplicate inclusion files. This article will focus on PHP's two functions get_include_path() and include_once() to introduce how to use them in combination to optimize file include path management.

1. Understand get_include_path() and include_once()

  • get_include_path()
    This function returns the include path (including_path) set in the current PHP environment. The include path is a list of directories that PHP searches for target files in when calling include or require- related functions.

  • include_once()
    include_once() is similar to include() and is used to include and execute code for a specified file. The difference is that include_once() will check whether the file has been included. If it is included, it will not be included again, preventing repeated execution of file content.

2. Why use it in combination?

Use include_once() to avoid errors caused by duplicate content, such as function redefinition or variable overwriting. Combined with get_include_path() , we can dynamically view and manage included paths, making file references more flexible and standardized.

For example, some public class libraries or configuration files in a project are placed in multiple directories, and by configuring the inclusion path, you do not need to write the full path each time, just write the file name to include it.

3. Specific examples

Assume that the project structure is as follows:

 /project
    /libs
        helper.php
    /config
        settings.php
    index.php

Set the include path and use include_once()

 <?php
// 1. Setting Included Path，Add to libs and config Table of contents
set_include_path(get_include_path() . PATH_SEPARATOR . __DIR__ . '/libs' . PATH_SEPARATOR . __DIR__ . '/config');

// 2. Output currently contains path，Confirm the setup is successful
echo "Currently included path：" . get_include_path() . "\n";

// 3. Introduced helper.php and settings.php document，Avoid duplicate inclusion
include_once 'helper.php';
include_once 'settings.php';

// 4. Business code...
?>

In this way, when calling include_once 'helper.php' or include_once 'settings.php' anywhere in the future, PHP will look for the corresponding file in the specified path, which reduces the hassle of writing full paths and reduces the risk of file not being found due to path errors.

4. Things to note

  • When adding paths through set_include_path() , be sure to use PATH_SEPARATOR to connect multiple directories to ensure compatibility with different operating systems (Windows is a semicolon ; Linux/macOS is a colon :) .

  • Although include_once() avoids repeated inclusion, it still needs to organize the code reasonably to prevent performance degradation from being caused by excessive repeated calls to files.

  • You can use get_include_path() to debug or dynamically adjust the path to improve flexibility.

5. Summary

Combining get_include_path() and include_once() , PHP developers can easily manage include paths, simplify file reference operations, and ensure the security and robustness of their code. Especially in large-scale projects, this method can significantly improve the maintainability and development efficiency of the code.

 <?php
// Setting Included Path
set_include_path(get_include_path() . PATH_SEPARATOR . __DIR__ . '/libs' . PATH_SEPARATOR . __DIR__ . '/config');

// Output currently contains path
echo "Currently included path：" . get_include_path() . "\n";

// use include_once 包含document，Prevent duplicate inclusion
include_once 'helper.php';
include_once 'settings.php';

// Sample function call
if (function_exists('helper_function')) {
    helper_function();
}
?>
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