Why would I use dirname FILE in an include or include once statement

Question

I have seen this     lt  php   include  dirname   FILE      DIRECTORY SEPARATOR    my file php      gt    Why would I ever need to do this  Why would I go to the trouble of getting the dirname and then concatenating that with a directory separator  and a new filename    Is the code above not equivalent to this     lt  php   include   my file php       gt        The PHP doc says       Files are included based on the file path given or  if none is given  the include path specified  If the file isn t found in the include path  include   will finally check in the calling script s own directory and the current working directory before failing  The include   construct will emit a warning if it cannot find a file  this is different behavior from require    which will emit a fatal error

User · Answer

I might have even a simpler explanation to this question compared to the accepted answer so I'm going to give it a go: Assume this is the structure of the files and directories of a project:

Project root directory:
                       file1.php
                       file3.php
                       dir1/
                            file2.php

(dir1 is a directory and file2.php is inside it)

And this is the content of each of the three files above:

//file1.php:
<?php include "dir1/file2.php"

//file2.php:
<?php include "../file3.php"

//file3.php:
<?php echo "Hello, Test!";

Now run file1.php and try to guess what should happen. You might expect to see "Hello, Test!", however, it won't be shown! What you'll get instead will be an error indicating that the file you have requested(file3.php) does not exist!

The reason is that, inside file1.php when you include file2.php, the content of it is getting copied and then pasted back directly into file1.php which is inside the root directory, thus this part "../file3.php" runs from the root directory and thus goes one directory up the root! (and obviously it won't find the file3.php).

Now, what should we do ?!

Relative paths of course have the problem above, so we have to use absolute paths. However, absolute paths have also one problem. If you (for example) copy the root folder (containing your whole project) and paste it in anywhere else on your computer, the paths will be invalid from that point on! And that'll be a REAL MESS!

So we kind of need paths that are both absolute and dynamic(Each file dynamically finds the absolute path of itself wherever we place it)!

The way we do that is by getting help from PHP, and dirname() is the function to go for, which gives the absolute path to the directory in which a file exists in. And each file name could also be easily accessed using the __FILE__ constant. So dirname(__FILE__) would easily give you the absolute (while dynamic!) path to the file we're typing in the above code. Now move your whole project to a new place, or even a new system, and tada! it works!

So now if we turn the project above to this:

//file1.php:
<?php include(dirname(__FILE__)."/dir1/file2.php");

//file2.php:
<?php include(dirname(__FILE__)."/../file3.php");

//file3.php:
<?php echo "Hello, Test!";

if you run it, you'll see the almighty Hello, Test!! (hopefully, if you've not done anything else wrong).

It's also worth mentioning that from PHP5, a nicer way(with regards to readability and preventing eye boilage!) has been provided by PHP as well which is the constant __DIR__ which does exactly the same thing as dirname(__FILE__)!

Hope that helps.

User · Answer

Let s say I have a  fake  directory structure like       root           app             bootstrap php          scripts             something                  somescript php          public             index php   Now assume that bootstrap php has some code included for setting up database connections or some other kind of boostrapping stuff   Assume you want to include a file in boostrap php s folder called init php   Now  to avoid scanning the entire include path with include  init php   you could use include    init php    There s a problem though  That    will be relative to the script that included bootstrap php  not bootstrap php   Technically speaking  it will be relative to the working directory    dirname   FILE    allows you to get an absolute path  and thus avoid an include path search  without relying on the working directory being the directory in which bootstrap php resides    Note  since PHP 5 3  you can use   DIR   in place of dirname   FILE       Now  why not just use include  init php      As odd as it is at first though    is not guaranteed to be in the include path   Sometimes to avoid useless stat   s people remove it from the include path when they are rarely include files in the same directory  why search the current directory when you know includes are never going to be there     Note  About half of this answer is address in a rather old post  What  39 s better of require dirname   FILE      39    39    39 myParent php  39   than just require   39 myParent php  39

User · Answer

I used this below if this is what you are thinking  It it worked well for me     lt  php     include   SERVER  DOCUMENT ROOT     head lib php     gt    What I was trying to do was pulla file called  head lib php from the root folder  It would not pull anything to build the webpage  The header  footer and other key features in sub directories would never show up  Until I did above it worked like a champ

User · Answer

If you want code is running on multiple servers with different environments then we have need   to use dirname FILE  in an include or include once statement   reason is follows  1  Do not give absolute path to include files on your server  2  Dynamically calculate the full path like absolute path   Use a combination of dirname FILE  and subsequent calls to itself until you reach to the home of your   myfile php    Then attach this variable that contains the path to your included files

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