[php] URL rewriting with PHP

If you only want to change the route for picture.php then adding rewrite rule in .htaccess will serve your needs, but, if you want the URL rewriting as in Wordpress then PHP is the way. Here is simple example to begin with.

Folder structure

There are two files that are needed in the root folder, .htaccess and index.php, and it would be good to place the rest of the .php files in separate folder, like inc/.

root/
  inc/
  .htaccess
  index.php

.htaccess

RewriteEngine On
RewriteRule ^inc/.*$ index.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ index.php [QSA,L]

This file has four directives:

1. RewriteEngine - enable the rewriting engine
2. RewriteRule - deny access to all files in inc/ folder, redirect any call to that folder to index.php
3. RewriteCond - allow direct access to all other files ( like images, css or scripts )
4. RewriteRule - redirect anything else to index.php

index.php

Because everything is now redirected to index.php, there will be determined if the url is correct, all parameters are present, and if the type of parameters are correct.

To test the url we need to have a set of rules, and the best tool for that is a regular expression. By using regular expressions we will kill two flies with one blow. Url, to pass this test must have all the required parameters that are tested on allowed characters. Here are some examples of rules.

$rules = array( 
    'picture'   => "/picture/(?'text'[^/]+)/(?'id'\d+)",    // '/picture/some-text/51'
    'album'     => "/album/(?'album'[\w\-]+)",              // '/album/album-slug'
    'category'  => "/category/(?'category'[\w\-]+)",        // '/category/category-slug'
    'page'      => "/page/(?'page'about|contact)",          // '/page/about', '/page/contact'
    'post'      => "/(?'post'[\w\-]+)",                     // '/post-slug'
    'home'      => "/"                                      // '/'
);

Next is to prepare the request uri.

$uri = rtrim( dirname($_SERVER["SCRIPT_NAME"]), '/' );
$uri = '/' . trim( str_replace( $uri, '', $_SERVER['REQUEST_URI'] ), '/' );
$uri = urldecode( $uri );

Now that we have the request uri, the final step is to test uri on regular expression rules.

foreach ( $rules as $action => $rule ) {
    if ( preg_match( '~^'.$rule.'$~i', $uri, $params ) ) {
        /* now you know the action and parameters so you can 
         * include appropriate template file ( or proceed in some other way )
         */
    }
}

Successful match will, since we use named subpatterns in regex, fill the $params array almost the same as PHP fills the $_GET array. However, when using a dynamic url, $_GET array is populated without any checks of the parameters.

    /picture/some+text/51

    Array
    (
        [0] => /picture/some text/51
        [text] => some text
        [1] => some text
        [id] => 51
        [2] => 51
    )

    picture.php?text=some+text&id=51

    Array
    (
        [text] => some text
        [id] => 51
    )

These few lines of code and a basic knowing of regular expressions is enough to start building a solid routing system.

Complete source

define( 'INCLUDE_DIR', dirname( __FILE__ ) . '/inc/' );

$rules = array( 
    'picture'   => "/picture/(?'text'[^/]+)/(?'id'\d+)",    // '/picture/some-text/51'
    'album'     => "/album/(?'album'[\w\-]+)",              // '/album/album-slug'
    'category'  => "/category/(?'category'[\w\-]+)",        // '/category/category-slug'
    'page'      => "/page/(?'page'about|contact)",          // '/page/about', '/page/contact'
    'post'      => "/(?'post'[\w\-]+)",                     // '/post-slug'
    'home'      => "/"                                      // '/'
);

$uri = rtrim( dirname($_SERVER["SCRIPT_NAME"]), '/' );
$uri = '/' . trim( str_replace( $uri, '', $_SERVER['REQUEST_URI'] ), '/' );
$uri = urldecode( $uri );

foreach ( $rules as $action => $rule ) {
    if ( preg_match( '~^'.$rule.'$~i', $uri, $params ) ) {
        /* now you know the action and parameters so you can 
         * include appropriate template file ( or proceed in some other way )
         */
        include( INCLUDE_DIR . $action . '.php' );

        // exit to avoid the 404 message 
        exit();
    }
}

// nothing is found so handle the 404 error
include( INCLUDE_DIR . '404.php' );