# Adding a Custom File Handler Sometimes it is convenient to “fake” a file — the browser has requested a file, but it it needs to be generated or processed before it is sent out. This can easily be done using a combination of the `.htacces` file and PHP. `.htaccess` is a configuration file which is read every time Apache serves a file. It allows you to pre-process requests. The configuation is inherited by sub-directories. If a sub-directory also contains a `.htacess` file, its settings will combine with or override those of the higher directory. ## The Technique {#technique} You can use `.htaccess` to dynamically (re)interpret types of files. In this case, we will use it to interpret exactly one file. To do so, we use the `Files` directive: ```apacheconf # .htaccess ``` This indicates that a request for `file.ext` will be interpreted or processed. Here, we will __rewrite__ it to call a PHP script: ```apacheconf # .htaccess RewriteEngine On RewriteRule ^(.+)$ doit.php [QSA,L] ``` - The pattern `^(.+)$` roughly means rewrite the _whole_ request. - `doit.php` will be the name of the PHP script to run. You can also include an absolute path, from the web root directory. - `[QSA,L]` will also pass on any query string which might have been included. Roughly, the rule means: `file.ext` ➔ `doit.php` That’s it. All you need now is a PHP script to process things. ### The Benefits So, what’s the benefit of this technique? Basically it allows you to generate a _virtual_ file which is really the result of a PHP script. For example: - `random.jpg` could be used to return a random image - `styles.css` could be used to return dynamically created CSS - `news.txt` could be used to return the latest or a random item of news In each case, the browser requests what _appears_ to be a static file. ## Example: Random Image Here we will intercept a request to `random.jpg` go return a random image from a specific directory. The `.htaccess` file is mostly the same. We will use the name of a notional image, `random.jpg`, though it could have been anything: ```apacheconf # /images/.htaccess RewriteEngine On RewriteRule ^(.+)$ /images/random.php [QSA,L] ``` Here the `.htaccess` file is placed inside the `images` directory, and the script will be called via `/images/random.jpg`. This will, in fact run the script `/images/random.php`. For the PHP script: - read the file names in a a predefined directory: ```php $images=glob("$root/images/slides/*.jpg"); ``` - Load a random Image: ```php $image=imagecreatefromjpeg($images[array_rand($images)]); ``` - Send the appropriate header, and output the image: ```php header('Content-Type: image/jpeg'); imagejpeg($image); ``` This give us: ```php ```