Search Engine-Friendly URLs

Method 2: .htaccess Error Pages

Implementation:

The second method involves using the .htaccess file. If you're new to it, .htaccess is a file used to administer Apache access options for whichever directory you place it in. The server administrator has a better method of doing this using his or him configuration files, but since most of us don't own our own server, we don't have control over what the server administrator does. Now, the server admin can configure what users can do with their .htaccess file so this approach may not work on your particular server, however in most cases it will. If it doesn't, you should contact your server administrator.

This method takes advantage of .htaccess’ ability to do error handling. In the .htaccess file in whichever directory you wish to apply this method to, simply insert the following line:

ErrorDocument 404 /processor.php

Now make a script called processor.php and put it in that same directory, and you're done! Lets say you have the following URL: http://www.domain.com/directory/999/12/. And again in this example "999" and "12" do not exist, however, as you don't specify a script anywhere in the directory path, Apache will create a 404 error. Instead of sending a generic 404 header back to the browser, Apache sees the ErrorDocument command in the .htaccess file and calls up processor.php.

Now, in the first example we used the $PATH_INFO variable, but that won’t work this time. Instead we need to use the $REQUEST_URI variable, which contains everything in the URL after the domain. So in this case, it contains: /directory/999/12/.

The first thing you need to do in processor.php is send a new HTTP header. Remember, Apache thought this was a 404 error, so it wants to tell the browser that it couldn’t find a page.

So, put the following line in your processor.php:

header("HTTP/1.1 200 OK");

At this time I need to point out an important fact. In the first example you could specify what script processed your URL. In this example all URLs must be processed by the same script, processor.php, which makes things a little different. Instead of creating different URLs based on what you want to do, such as article.php/999/12 or printarticle.php/999/12 you only have 1 script that must do both.

So you must decide what to do based on the information processor.php receives - more specifically, by counting how many parameters are passed. For instance on my site, I use this method to generate my pages: I know that if there's just one parameter, such as http://www.online-literature.com/shakespeare/, that I need to load an author information page; if there are 2 parameters, such as http://www.online-literature.com/shakespeare/hamlet/, I know that I need to load a book information page; and finally if there are 3 parameters, such as http://www.online-literature.com/shakespeare/hamlet/3/, I know I need to load a chapter viewing page. Alternatively, you can simply use the first parameter to indicate the type of page to display, and then process the remaining parameters based on that.
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There are 2 ways you can accomplish this task of counting parameters. First you need to use PHP’s explode function to divide up the $REQUEST_URI variable. So if $REQUEST_URI = /shakespeare/hamlet/3/:

$var_array = explode("/",$REQUEST_URI);

Now note that, because of the positioning of the /’ there are actually 5 elements in this array. The first element, element 0, is blank, because it contains the information before the first /. The fifth element, element 4, is also blank, because it contains the information after the last /.

So now we need to count the elements in our $var_array. PHP has two functions that let us do this. We can use the sizeof() function as in this example:

$num = sizeof($var_array); // 5

You’ll notice that the sizeof() function counts every item in the array regardless of whether it's empty. The other function is count(), which is an alias for the sizeof() function.

Some search engines, like AOL, will automatically remove the trailing / from your URL, and this can cause problems if you’re using these functions to count your array. For instance http://www.online-literature.com/shakespeare/hamlet/ becomes http://www.online-literature.com/shakespeare/hamlet, and as there are 3 total elements in that array our processor.php would load an author page instead of a book page.

The solution is to create a function that will count only the elements in an array that actually hold data. This will allow you to leave off the ending / or allow any links from AOL'’s search engine to point to the proper place. An example of such a function is:

function count_all($arg)
{
// skip if argument is empty
if ($arg) {
// not an array, return 1 (base case)
if(!is_array($arg))
return 1;
// else call recursively for all elements $arg
foreach($arg as $key => $val)
$count += count_all($val);
return $count;
}
}

To get your count, access the function like this:

$num = count_all($url_array);

Once you know how many parameters you need, you can define them like this:

$author=$var_array[1];
$book=$var_array[2];
$chapter=$var_array[3];

Then you can use includes to call up the appropriate script, which will query your database and set up your page. Also if you get a result you’re not expecting, you can simply create your own error page for display to the browser.

Drawback:

The drawback of this method is that every page that's hit is seen by Apache as an error. Thus every hit creates another entry in your server error logs, which effectively destroys their usefulness. So if you use this method you sacrifice your error logs.