> Note: In PHP, `parse_ini_file()` seems to want strings to be between by quotes `"` in the ini file.
+### Register plugin's routes
+
+Shaarli lets you register custom Slim routes for your plugin.
+
+To register a route, the plugin must include a function called `function <plugin_name>_register_routes(): array`.
+
+This method must return an array of routes, each entry must contain the following keys:
+
+ - `method`: HTTP method, `GET/POST/PUT/PATCH/DELETE`
+ - `route` (path): without prefix, e.g. `/up/{variable}`
+ It will be later prefixed by `/plugin/<plugin name>/`.
+ - `callable` string, function name or FQN class's method to execute, e.g. `demo_plugin_custom_controller`.
+
+Callable functions or methods must have `Slim\Http\Request` and `Slim\Http\Response` parameters
+and return a `Slim\Http\Response`. We recommend creating a dedicated class and extend either
+`ShaarliVisitorController` or `ShaarliAdminController` to use helper functions they provide.
+
+A dedicated plugin template is available for rendering content: `pluginscontent.html` using `content` placeholder.
+
+> **Warning**: plugins are not able to use RainTPL template engine for their content due to technical restrictions.
+> RainTPL does not allow to register multiple template folders, so all HTML rendering must be done within plugin
+> custom controller.
+
+Check out the `demo_plugin` for a live example: `GET <shaarli_url>/plugin/demo_plugin/custom`.
+
+### Understanding relative paths
+
+Because Shaarli is a self-hosted tool, an instance can either be installed at the root directory, or under a subfolder.
+This means that you can *never* use absolute paths (eg `/plugins/mything/file.png`).
+
+If a file needs to be included in server end, use simple relative path:
+`PluginManager::$PLUGINS_PATH . '/mything/template.html'`.
+
+If it needs to be included in front end side (e.g. an image),
+the relative path must be prefixed with special data:
+
+ * if it's a link that will need to be processed by Shaarli, use `_BASE_PATH_`:
+ for e.g. `$data['_BASE_PATH_'] . '/admin/tools`.
+ * if you want to include an asset, you need to add the root URL (base path without `/index.php`, for people using Shaarli without URL rewriting), then use `_ROOT_PATH_`:
+ for e.g
+`$['_ROOT_PATH_'] . '/' . PluginManager::$PLUGINS_PATH . '/mything/picture.png`.
+
+Note that special placeholders for CSS and JS files (respectively `css_files` and `js_files`) are already prefixed
+with the root path in template files.
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