Question

I’ve had to pick up a web app built with Drupal – I need to edit a link that is on the front end. It is a single page app – but when I open index.php there is a link to a bootstrap.inc which contains over 11000 lines of code none of which relate to the front end.

Answer 1

In Drupal, index.php is a router. It gets a request from the server, with the path added to it. It then routes the request through many (complex) layers to create the HTML.

I suggest you read up on the basics of Drupal before diving head-first into the application.

Based on your question, you seem to completely misunderstand the basics of Drupals routing, to beging with.

• Request /foo/bar arrives at Apache
• Apache calls `index.php?q=foo/bar
• Drupal gets bootstrapped.
• Drupal loads the menu-system.
• Drupal looks up, if there is a menu-router to handle “foo/bar”. Or one of the parents to fall back on (“foo” in this case).
• If found, Drupal will call the callback for that page: for example my_bar.module implements hook_menu and registers “foo/bar” with callback my_bar_page. This function is available in this module.
• my_bar_page is called. Its output should be HTML.
• Drupal loads the theme layer, and passes the received HTML as $content into the page template. (amongst others, it also loads the block system, adds footers and does loads of complex preprocessing on all the page variables).

Note that this is a very much simplified version of what actually goes on. The reality is a gigantic (spaggetti, some might say) of callbacks, caching layers, hooks and theme-layers.