Absolute & Relative Paths In PHP (A Simple Guide)

Welcome to a quick tutorial on absolute and relative paths in PHP. So you have set a verified file path, but PHP is still complaining about “missing” files and folders? Yes, it is easy to get lost in absolute and relative paths in PHP.

The covers the basics, but let us walk through more on how file paths work in PHP – Read on!

ⓘ I have included a zip file with all the source code at the start of this tutorial, so you don’t have to copy-paste everything… Or if you just want to dive straight in.

 

 

TLDR – QUICK SLIDES

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TABLE OF CONTENTS

 

 

1) ABSOLUTE & RELATIVE PATH

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

<?php
// (A) ABSOLUTE PATH (FULL PATH)
require "D:\\http\\1a-dummy.php";
 
// (B) RELATIVE PATH (BASED ON CURRENT WORKING DIRECTORY)
// if this script is placed at "D:\http\1b-abs-rel.php"
// current working directory (cwd) will be "D:\http"
// this relative path will resolve to "D:\http\1a-dummy.php"
require "1a-dummy.php";

As in the introduction above:

• An absolute file path is simply the “full file path”. Although a bit long-winded, it’s hard to mess up with this one.
• On the other hand, the relative file path is based on the current working directory.

But just what the heck is the “current working directory”? Follow up with the next example.

 

 

2) CURRENT WORKING DIRECTORY (CWD)

<?php
// (A) GET CWD
// if this script is placed at "D:\http\2-cwd.php"
// cwd will be "D:\http"
echo getcwd() . "<br>";

In simple terms, the current working directory is the folder where the script is placed in. We can easily get the current working directory with the getcwd() function.

 

3) CONFUSION WITH THE CURRENT WORKING DIRECTORY

// (A) CWD IS BASED ON THE FIRST SCRIPT!
// if this script is placed at "D:\http\inside\3-cwd.php"
// cwd is "D:\http\inside"
require "D:\\http\\2-cwd.php";

So far so good with relative paths? Now comes the part that destroyed many beginners, take note that this example script is placed at D:\http\inside. Guess what getcwd() shows when we run this example? Yes, the current working directory now changes to D:\http\inside. Keep in mind, the current working directory is fixed to the first script that runs.

 

 

4) CHANGING THE WORKING DIRECTORY

<?php
// (A) SHOW CURRENT WORKING DIRECTORY
// if this script is placed at "D:\http\inside\4-change-cwd.php"
// cwd is "D:\http\inside"
require "D:\\http\\2-cwd.php";
 
// (B) CHANGE CWD TO PARENT FOLDER
// if original cwd is "D:\http\inside"
// changing the cwd to the parent will become "D:\http\"
chdir("../");
echo getcwd(); 

The current working directory will surely mess up a lot of relative paths. So, how do we fix this problem? Thankfully, we can use the chdir() function to change the current working directory.

 

5) MAGIC CONSTANTS

<?php
// (A) CURRENT FILE
// if this file is placed at "D:\http\5-magic.php"
// __FILE__ is "D:\http\5-magic.php"
echo __FILE__ . "<br>";
 
// (B) CURRENT FOLDER
// if this file is placed at "D:\http\5-magic.php"
// __DIR__ is "D:\http"
echo __DIR__ . "<br>";

Even if we are able to change the working directory, relative paths are still messy in big projects. I will recommend using magic constants instead.

• __FILE__ is the full path and file name where the current script is located.
• __DIR__ is the folder where the current script is located.

 

 

6) MAGIC CONSTANTS VS WORKING DIRECTORY

<?php
// (A) CURRENT FILE
// if this file is placed at "D:\http\inside\6-magic.php"
// __FILE__ is "D:\http\inside\6-magic.php"
echo __FILE__ . "<br>";
 
// (B) CURRENT FOLDER
// if this file is placed at "D:\http\inside\6-magic.php"
// __DIR__ is "D:\http\inside"
echo __DIR__ . "<br>";
 
// (C) GET PARENT FOLDER
$parent = dirname(__DIR__) . DIRECTORY_SEPARATOR;
require $parent . "5-magic.php";

To lessen the confusion, take note that the magic constants are different from the current working directory.

• The current working directory is based on the first script that we run.
• Magic constants are based on where the scripts are placed in.

Yes, magic constants are the better way to do “pathfinding”, and to build absolute paths.

 

 

7) MORE PATH YOGA

<?php
// (A) SERVER PATH VARIABLES
// if this file is placed at "D:\http\7-extra.php"
echo $_SERVER["DOCUMENT_ROOT"] . "<br>"; // D:\http
echo $_SERVER["PHP_SELF"] . "<br>"; // 7-extra.php
echo $_SERVER["SCRIPT_FILENAME"] . "<br>"; // D:/http/7-extra.php
 
// (B) PATH INFO
$parts = pathinfo("D:\\http\inside\\index.php");
echo $parts["dirname"] . "<br>"; // D:\http\inside
echo $parts["basename"] . "<br>"; // index.php
echo $parts["filename"] . "<br>"; // index
echo $parts["extension"] . "<br>"; // php
 
// (C) BASENAME
$path = "D:\\http\\inside";
echo basename($path) . "<br>"; // inside
$path = "D:\\http\\inside\\foo.php";
echo basename($path) . "<br>"; // foo.php
$path = "D:\\http\\inside\\foo.php";
echo basename($path, ".php") . "<br>"; // foo
 
// (D) DIRNAME
$path = "D:\\http\\inside\\";
echo dirname($path) . "<br>"; // D:\http
echo dirname($path, 2) . "<br>"; // D:\
 
// (E) REALPATH
echo realpath("") . "<br>"; // D:\http
echo realpath("../") . "<br>"; // D:\

Finally, this is a quick crash course on the various variables and functions that may help you find the file path.

 

SERVER SUPERGLOBAL

• $_SERVER["DOCUMENT_ROOT"] – Contains the root HTTP folder.
• $_SERVER["PHP_SELF"] – The relative path to the script.
• $_SERVER["SCRIPT_FILENAME"] – The full path to the script.

 

PATH INFO

The PHP pathinfo() function will give you bearings on a given path:

• dirname – The directory of the given path.
• basename  – The filename with extension.
• filename – Filename, without extension.
• extension – File extension.

 

BASENAME

The basename() function will give you the trailing directory or file of a given path.

 

DIRNAME

The dirname() function will give you the parent directory of a given path.

 

REALPATH

The realpath() function gives you a canonicalized absolute path… Kind of useful, but still based on the current working directory.

 

 

 

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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) FORWARD OR BACKWARD SLASH?

In case you have not realized:

• Windows use \
• Linux and Mac uses /

Not really a big problem though, just use DIRECTORY_SEPARATOR in PHP and it will automatically resolve to the “correct slash”.

 

EXTRA) CASE SENSITIVE

Also, take extra note:

• We have a Foo.php script.
• Windows is not case-sensitive – require "FOO.PHP" will work.
• But Mac/Linux is case-sensitive – require "FOO.PHP" will throw a “file not found” error.

 

ALL THE PATH-RELATED VARIABLES

Variable	Description
__FILE__	The absolute path and file name of the current script.
__DIR__	The absolute path of the current script.
$_SERVER["DOCUMENT_ROOT"]	The root HTTP folder.
$_SERVER["PHP_SELF"]	Relative path to the script.
$_SERVER["SCRIPT_FILENAME"]	Full path (and filename) to the script.
DIRECTORY_SEPARATOR	This is automatically a forward or backward slash, depending on the system.

 

ALL THE PATH-RELATED FUNCTIONS

Function	Description
getcwd()	Returns the current working directory.
chdir()	Changes the current working directory.
pathinfo()	Gives you the path information of a given path. dirname – The directory of the given path. basename – The filename with extension. filename – Filename, without extension. extension – File extension.
basename()	Get the trailing directory or file of a given path.
dirname()	Get the parent directory of a given path.
realpath()	Canonicalized absolute path.

 

LINKS & REFERENCES

• PHP Magic Constants
• getcwd
• chdir
• dirname
• basename
• pathinfo
• realpath

 

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