Drupal also comes with user defined mass URL aliasing capabilities. You might like to see completely different URLs used by Drupal, or even URLs translated to the visitors' native language, in which case this feature is handy. Only an administrator with access to the website source code can set up this kind of aliases. You can define a function somewhere in your code (even in settings.php), following this example:

// Example for Drupal 4.6.x
function conf_url_rewrite($path, $mode = 'incoming') {
  if ($mode == 'incoming') { // URL coming from a client
    return preg_replace('!^display/(\d+)$!', 'node/\1', $path);
  }
  elseif ($mode == 'outgoing') { // URL going out to a client
    return preg_replace('!^node/(\d+)$!', 'display/\1', $path);
  }
}

// Example for Drupal 4.7.x and 5.x (NOT 6.x)
function custom_url_rewrite($type, $path, $original) {
  // This path was already aliased, skip rewriting it
  if ($path != $original) {
    return $path;
  }
  if ($type == 'source') { // URL coming from a client
    return preg_replace('!^display/(\d+)$!', 'node/\1', $path);
  }
  elseif ($type == 'alias') { // URL going out to a client
    return preg_replace('!^node/(\d+)$!', 'display/\1', $path);
  }
}

This function will shorten every node/$node_id type of URL to display/$node_id. Individual URL aliases defined on the browser interface of Drupal take precedence, so if you have a 'contact' page alias for example, then the display/3 alias will not be effective when outgoing links are created. Incoming URLs however always work with the mass URL aliased variant. Only two modes are supposed to be supported by your custom function.

You cannot only use this feature to shorten the URLs, or to translate them to your own language, but also to add completely new subURLs to an already existing module's URL space, or to compose a bunch of existing stuff together to a common URL space. You can create a news section for example aliasing nodes and taxonomy overview pages falling under a 'news' vocabulary, thus having news/15 and news/sections/3 instead of node/15 and taxonomy/term/3. You need extensive knowledge of Drupal's inner workings and regular expressions though to make such advanced aliases.

Again, this is an advanced Drupal feature which requires more than basic PHP knowledge to use. For most users, pathauto and related modules will meet their needs, and they require no experience with PHP or regular expressions.

Comments

beginner’s picture

beginner commented

Karoly just documented it at api.drupal.org:
http://api.drupal.org/api/HEAD/function/custom_url_rewrite
With more examples.

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mvc’s picture

mvc
they
Primary language English
Location Montréal, CA
commented

Ironically, this alias doesn't work anymore :)

Documentation for Drupal 5.x:
http://api.drupal.org/api/function/custom_url_rewrite/5

Documentation for Drupal 6.x:
http://api.drupal.org/api/function/custom_url_rewrite_outbound/6
http://api.drupal.org/api/function/custom_url_rewrite_inbound/6

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gonzalom’s picture

gonzalom commented

I looked in to the example in http://api.drupal.org/api/function/custom_url_rewrite/5

I change some thing and I get off the fourth arg "$path_language" because I got an error msg.

Finally, my function is:

function custom_url_rewrite($op, $result, $path) {
	//global $user;
	$items = array(
		array( 'source'=>'node', 		'alias'=>'articulo', 	'patron'=>'/^%item%(.*)$/', 	'result'=>'%item%\1'),
		array( 'source'=>'taxonomy', 	'alias'=>'categoria', 	'patron'=>'/^%item%(.*)$/', 	'result'=>'%item%\1'),
		array( 'source'=>'term', 		'alias'=>'termino', 	'patron'=>'/\/%item%\//', 		'result'=>'/%item%/'),
		array( 'source'=>'user', 		'alias'=>'usuario', 	'patron'=>'/^%item%(.*)$/', 	'result'=>'%item%\1'),
		array( 'source'=>'blog', 		'alias'=>'blog', 		'patron'=>'/^%item%(.*)$/', 	'result'=>'%item%\1'),
		array( 'source'=>'forum', 		'alias'=>'foro', 		'patron'=>'/^%item%(.*)$/', 	'result'=>'%item%\1'),
		array( 'source'=>'image', 		'alias'=>'imagen', 		'patron'=>'/^%item%(.*)$/', 	'result'=>'%item%\1'),
		array( 'source'=>'aggregator', 	'alias'=>'noticias', 	'patron'=>'/^%item%(.*)$/', 	'result'=>'%item%\1')
	);
	if ($op == 'alias') {
		// source to alias. Ej: node -> articulo
		$reemplazos = array();
		foreach( $items AS $item ) {
			$key = str_replace('%item%',$item['source'],$item['patron']);
			$value = str_replace('%item%',$item['alias'],$item['result']);
			$reemplazos[$key] = $value;
		}
		return preg_replace(array_keys($reemplazos), array_values($reemplazos), $path);
	}
	if ($op == 'source') {
		// alias to source. Ej: articulo -> node
		$reemplazos = array();
		foreach( $items AS $item ) {
			$key = str_replace('%item%',$item['alias'],$item['patron']);
			$value = str_replace('%item%',$item['source'],$item['result']);
			$reemplazos[$key] = $value;
		}
		return preg_replace(array_keys($reemplazos), array_values($reemplazos), $path);
	}
	// Return the default result
	return $result;
}

As you can see, you can specify a pattern for each item.
The most common pattern is '/^%item%(.*)$/', that only get the item if is in the beginning, but you may be interested in other patterns: "term" (like in taxonomy/term/3) is not at the beginning of the string, so it will not work with the most common pattern, this item will need a pattern like '/\/%item%\//'.

Yo can add as many items as you want, and you can also write a module to put them all through the admin.