Elgg has two mechanisms to respond to HTTP requests that don't already go through the :doc:`/design/actions` and :doc:`/guides/views/simplecache` systems.
After removing the site URL, Elgg splits the URL path by /
into an array. The first
element, the identifier, is shifted off, and the remaining elements are called the
segments. For example, if the site URL is http://example.com/elgg/
, the URL
http://example.com/elgg/blog/owner/jane?foo=123
produces:
Identifier: 'blog'
. Segments: ['owner', 'jane']
. (the query string parameters are
available via get_input()
)
The site URL (home page) is a special case that produces an empty string identifier and an empty segments array.
To handle all URLs that begin with a particular identifier, you can register a function to act as a :doc:`/guides/pagehandler`. When the handler is called, the segments array is passed in as the first argument.
The following code registers a page handler for "blog" URLs and shows how one might route the request to a resource view.
elgg_register_page_handler('blog', 'blog_page_handler');
function blog_page_handler(array $segments) {
// if the URL is http://example.com/elgg/blog/view/123/my-blog-post
// $segments contains: ['view', '123', 'my-blog-post']
$subpage = elgg_extract(0, $segments);
if ($subpage === 'view') {
// use a view for the page logic to allow other plugins to easily change it
set_input('guid', (int)elgg_extract(1, $segments));
echo elgg_view('resources/blog/view');
// in page handlers, return true says, "we've handled this request"
return true;
}
// ... handle other subpages
}
The route
plugin hook is triggered earlier, before page handlers are called. The URL
identifier is given as the type of the hook. This hook can be used to modify the identifier
or segments, to take over page rendering completely, or just to add some logic before the
request is handled elsewhere.
Generally devs should use a page handler unless they need to affect a single page or a wider variety of URLs.
The following code intercepts requests to the page handler for customblog
and internally redirects them
to the blog
page handler.
function myplugin_customblog_route_handler($hook, $type, $returnvalue, $params) {
// direct Elgg to use the page handler for 'blog'
$returnvalue['identifier'] = 'blog';
return $returnvalue;
}
elgg_register_plugin_hook_handler('route', 'customblog', 'myplugin_customblog_route_handler');
The following code results in /blog/all
requests being completely handled by the plugin hook handler.
For these requests the blog
page handler is never called.
function myplugin_blog_all_handler($hook, $type, $returnvalue, $params) {
$segments = elgg_extract('segments', $returnvalue, array());
if (isset($segments[0]) && $segments[0] === 'all') {
$title = "We're taking over!";
$content = elgg_view_layout('one_column', array(
'title' => $title,
'content' => "We can take over page rendering completely"
));
echo elgg_view_page($title, $content);
// in the route hook, return false says, "stop rendering, we've handled this request"
return false;
}
}
elgg_register_plugin_hook_handler('route', 'blog', 'myplugin_blog_all_handler');
For regular pages, Elgg's program flow is something like this:
- A user requests
http://example.com/blog/owner/jane
. - Plugins are initialized.
- Elgg parses the URL to identifier
blog
and segments['owner', 'jane']
. - Elgg triggers the plugin hook
route, blog
(see above). - Elgg finds a registered page handler (see above) for
blog
, and calls the function, passing in the segments. - The page handler function determines it needs to render a single user's blog. It stores the username
via
set_input()
and calls the viewresources/blog/owner
. - The
resources/blog/owner
view gets the username viaget_input()
, and uses many other views and formatting functions likeelgg_view_layout()
andelgg_view_page()
to create the entire HTML page. - The page handler echos the view HTML and returns
true
to indicate it handled the request. - PHP invokes Elgg's shutdown sequence.
- The user receives a fully rendered page.
Elgg's coding standards suggest a particular URL layout, but there is no syntax enforced.