[AndrewD]

Originally Posted by karlm

Can someone define exactly what a hook is, what it's job is and how it functions? Perhaps an analogy to assist with the less vb orientated folk, such as my good self

A hook provides a way for others to insert extra php code into standard product code without them having to edit any of the product's files. The programmer inserts hooks in two steps:

a) a line at the relevant place in the php code file which takes the form

PHP Code:

    ($hook = vBulletinHook::fetch_hook('hookname')) ? eval($hook) : false; 


and
b) a line in the file includes/hooks_productname.xml, which defines all the hooks that are available.

As an example, there is a hook called cache_templates in the file global.php. This hook appears just before vbulletin caches the required templates. So if someone (e.g. the author of a product that integrates within vbulletin) wants to cache another template, she can use that hook to do so, in this case, by writing a plugin which is tied to the cache_templates hook, containing the following code:

PHP Code:

    if (is_array($globaltemplates)) {
        $globaltemplates[] = 'my_template';
    } 


When the global.php code is executed and reaches the cache_templates hook, it will automatically execute this plugin code (and any other plugins tied to the same hook).

Hooks and plugins are widely used in software products to allow the products to be extended without having to modify the main code files.