Include File From Another Folder In PHP (Simple Examples)

Welcome to a short tutorial on how to include files from other folders in PHP. Need to load another file in PHP, but it is in a different folder? No problem, it is a very simple fix.

That covers the quick basics, but let us walk through more details on how “paths” work in PHP – Read on!

TLDR – QUICK SLIDES

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TABLE OF CONTENTS

PHP Include Path

Download & Notes

Extra Bits & Links

The End

1) ABSOLUTE VS RELATIVE FILE PATH

<?php
// (A) ABSOLUTE PATH (FULL PATH)
include "D:\\http\\1b-demo.php";
 
// (B) RELATIVE PATH (BASED ON CWD)
// if this script is placed in "D:\http\1a-demo.php"
// cwd will be "D:\http"
// this will resolve to "D:\http\1b-demo.php"
include "1b-demo.php";

<?php
echo "Hello!<br>";

First, a quick introduction to 2 terms:

• Absolute Path – The full path to the file.
• Relative Path – A “short-hand” path that is based on the current working directory.

Yep, the absolute path should be self-explanatory. But the relative path is the one that confuses most beginners.

2) WHAT IS THE CURRENT WORKING DIRECTORY?

<?php
// (A) GETCWD() TO GET THE CURRENT WORKING DIRECTORY
// if this script is placed in "D:\http\2-demo.php"
// cwd will be "D:\http"
echo getcwd() . "<br>";
 
// (B) ALL RELATIVE PATHS ARE BASED ON CWD
// if cwd is "D:\http"
// this will resolve to "D:\http\1b-demo.php"
include "1b-demo.php";

Just what is the “current working directory”? We can do a quick check with getcwd(), and it is simply the folder where the script is located in. For this example:

• 2-demo.php is placed inside D:\http.
• Accessing http://site.com/2-demo.php will set the current working directory to D:\http.
• Relative paths depend on the current working directory.
  • include "1b-demo.php" will resolve to D:\http\1b-demo.php.
  • include "lib/SCRIPT.php" will resolve to D:\http\lib\SCRIPT.php.

3) THE CONFUSING CURRENT WORKING DIRECTORY

<?php
// (A) CWD IS FIXED TO THE FIRST SCRIPT!
include "lib/3b-inside.php";

<?php
// (B) THE CWD CONFUSION
// assuming files placed at - D:\http\3a-outside.php and D:\http\lib\3b-inside.php
// if accessed from "http://site.com/3a-outside.php" - cwd is "d:\http"
// if accessed from "http://site.com/lib/3b-inside.php" - cwd is "d:\http\lib"
echo getcwd();

Ready for the confusing part about the current working directory?

• Take note of where the scripts are placed – D:\http\3a-outside.php and D:\http\lib\3b-inside.php.
• If we access http://site.com/3a-outside.php, the current working directory is set to D:\http.
• But when we access http://site.com/lib/3b-inside.php, the current working directory is set to D:\http\lib instead.

Yes, the current working directory is fixed to the first script. This is a common pitfall among beginners, not knowing how the current working directory works.

4) PHP MAGIC CONTANTS

<?php
// (A) RELATIVE PATH
// assuming - "D:\http\4a-outside.php"
// this will resolve to "D:\http\lib\4b-inside.php"
include "lib/4b-inside.php";

// (B) CWD VS MAGIC CONSTANTS
// assuming - "D:\http\4a-outside.php" and "D:\http\lib\4b-inside.php"
// accessing http://site.com/4a-outside.php
// cwd will be "D:\http"
// __DIR__ will be "D:\http\lib"
// __FILE__ will be "D:\http\lib\4b-inside.php"
echo getcwd() . "<br>";
echo __DIR__ . "<br>";
echo __FILE__ . "<br>";

If you want to refer to the current script itself, use the __DIR__ and __FILE__ magic constants instead. Take note of how this works:

• Scripts are placed at D:\http\4a-outside.php and D:\http\lib\4b-inside.php.
• Accessing http://site.com/4a-outside.php will set the CWD to D:\http.
• But in 4b-inside.php:
  • __DIR__ refers to where 4b-inside.php is sitting in – Which is D:\http\lib.
  • __FILE__ is the full absolute path of 4b-inside.php.

5) SEMI-AUTOMATIC ABSOLUTE PATH

<?php
// (A) LOAD CONFIG FILE
// assuming "D:\http\5a-path.php"
// this will resolve to "D:\http\lib\5b-config.php"
require __DIR__ . "/lib/5b-config.php";
echo PATH_BASE;
echo PATH_LIB;

// (B) USE PREDEFINED ABSOLUTE PATHS
include PATH_BASE . "1b-demo.php";
include PATH_LIB . "4b-inside.php";

<?php
// (C) AUTOMATIC ABSOLUTE PATH
// assuming "D:\http\lib\5b-config.php"
// PATH_LIB will be "D:\http\lib\"
// PATH_BASE will be "D:\http\"
define("PATH_LIB", __DIR__ . DIRECTORY_SEPARATOR);
define("PATH_BASE", dirname(__DIR__) . DIRECTORY_SEPARATOR);

What is the most reliable way to deal with file paths then? What I usually do:

• Structure the project properly, keep the config and library files in a protected lib folder.
• Create a lib/config.php to contain the database settings, secret keys, and file paths.
• In lib/config.php, define("PATH_LIB", __DIR__ . DIRECTORY_SEPARATOR) will contain the absolute path of the lib folder.
• Then, define("PATH_BASE", dirname(__DIR__) . DIRECTORY_SEPARATOR) will contain the absolute base path of the project (parent of lib folder).

That’s all. After loading the config file, require PATH_LIB . "LIBRARY.PHP" and include PATH_ROOT . "FILE.EXT" is now an absolute file path that can never go wrong.

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EXAMPLE CODE DOWNLOAD

Click here for the source code on GitHub gist, just click on “download zip” or do a git clone. I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

EXTRA) SLASHES & CASE SENSITIVE

Lastly, a small word of reminder –

• Windows uses \
• Linux/Mac uses /
• Does not quite matter, since modern OS will automatically parse the slash. Just use DIRECTORY_SEPARATOR if not sure, this will automatically resolve to the “correct slash”.
• Windows is not case-sensitive. require "Foo.php" and require "FOO.PHP" does not matter.
• Linux/Mac is case-sensitive. require "Foo.php" and require "FOO.PHP" refers to 2 different files.

REFERENCES & LINKS

• Official PHP manual – require
• Official PHP manual – include
• require_once
• include_once
• Absolute & Relative Path In PHP – Code Boxx

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