When PHP's dirname() saved the day

Apr 24, 2009 php scripting
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Now, I won’t bore you with the actual details of how I came across this - let’s just skip to the explanation and example:

First, even when it makes ‘sense’, you should not be using relative paths in your command line PHP scripts. I am so used to writing web PHP that I fell into this bad habit.

Show Me Why dirname() is your hero

Imagine a directory structure on windows like this:

C:\DEVELOPMENT\local>dir
 Volume in drive C has no label.
 Volume Serial Number is 1122-45E1

 Directory of C:\DEVELOPMENT\local

04/23/2009  08:40 PM    <dir>          .
04/23/2009  08:40 PM    <dir>          ..
04/23/2009  08:37 PM    <dir>          includes
04/23/2009  08:40 PM    <dir>          testdirname
               0 File(s)                    0 bytes
               4 Dir(s)  67,484,995,584 bytes free

We have two files:

testdirname/script.php 
<?php
require_once '../includes/include.php';
print "I've done ran, ya'll.";
includes/include.php 
<?php
print "I'm an include!\n";

Now, let’s run the script as it is:

C:\DEVELOPMENT\local\testdirname>php script.php
I'm an include!
I've done ran, ya'll.

Not too bad - but note how we’re actually in the script.php’s working directory. What if we wanted to run it in a different directory?

C:\DEVELOPMENT\local>php testdirname\script.php

Warning: require_once(../includes/include.php): failed to open stream: No such file or directory in C:\DEVELOPMENT\local\testdirname\script.php on line 2

Well this makes sense because I programmed with that relative path.

Instead, change the require line in script.php to this:

require_once dirname(__FILE__) . '/../includes/include.php';

This way, it always gets the full directory of the file itself (__FILE__ constant) - and THEN you can path to the file any which way you’d like.

Let’s check the output:

C:\DEVELOPMENT\local>php testdirname\script.php
I'm an include!
I've done ran, ya'll.

Yep - I KNOW - Simple. Its embarrassing to say it bit me - but it did :)

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