Re: Full versus relative URLs

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On Wed, Feb 18, 2009 at 12:05:21PM -0500, PJ wrote:

> Stuart wrote:
> > 2009/2/18 PJ <af.gourmet@xxxxxxxxxxxx>:
> >
> >> Stuart wrote:
> >>
> >>>>> <?php include dirname(__FILE__)."/../header.php"; ?>
> >>>>>

<snip>

> >
> >
> What confused me here is that often, in examples, there are all sorts of
> references to files and there seems to be no standard as to how to refer
> to them in non-scripts such as these e-mails. So, I thought that
> dirname(_FILE_) was a general reference to a directory name and a
> file... :-(
> I don't want to defend myself here, but I cannot be expected to know all
> functions and look up anything that might resemble a function...
> I still do not understand, and that is the keyword here, I am trying to
> understand things - what does /../header.php mean. I know the 2 dots
> mean a higher directory in Unix... but I understood that ../ would mean
> the root directory - so what is the / before the ../header.php mean?
> When including scripts or pages, i find that if I am referencing to the
> current directory, just the filename or /filename works. If the
> reference is up a level, ../ works
> 
> e.g. to reference root/images/ from root/authors = ../images/file.ext
> from root = /images/file.ext or images/file.ext
> 
> I haven't needed to go to a deeper level yet.

Let's break it down: dirname(__FILE__) . "/../header.php";

__FILE__ is a constant that represents the filename of whatever file
it's in. This filename includes the directory to the file.

dirname() parses out just the directory for the filename passed as a
parameter.

The "." is, of course, the "concatenate" parameter for PHP. So we're
going to add on whatever comes after the directory for the file.

"/../header.php"

This one is a little trickier. We want a file called header.php, but
it's in a directory just above where you are. In Unix/Linux (and
therefore most internet servers), "../header.php" represents a file
called header.php in the directory just above where you are. Now, you'll
notice that what's quoted is "/../header.php", not "../header.php".
There's a leading slash there. Why? That's because we're going to append
it to a directory which has no leading slash. So if dirname(__FILE__)
yields "/var/www/includes", and you just add "../header.php" to it,
you'd get: /var/www/includes../header.php, not the file you want. The
file you want is: /var/www/includes/../header.php. And in this case,
header.php actually resides in /var/www (one directory up from
/var/www/includes).

Paul
-- 
Paul M. Foster

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