Question

The question is about functions and arguments in PHP. I am reading code of simple extension for mediawiki.
It adds callback function:

$wgHooks['ArticleSaveComplete'][] = 'fnAutoWikiDump';

and then there is definition of this function:

function fnAutoWikiDump(&$article, &$user, &$text, &$summary, &$minoredit, 
                    &$watchthis, &$sectionanchor, &$flags, &$revision){...}

inside this function I can access members of class $article:

$awd_title = $article->getTitle();

I cannot understand how variable $article was passed to the function while calling it? It looks like it was passed in definition of the function (I know it is wrong), but I don’t understand how it was passed.
Do you?

Answer 1

The code you have posted, and the sample code in the link do not show the details of actually calling the function. It is merely registered as a callback. Part of the usefulness of callback functions is that you typically do not have to call them yourself at all, but rather they are called automatically by the process that uses them.

Somewhere else in the MediaWiki code, where the callbacks registered with ArticleSaveComplete are called (there’s an array of them), the correct parameters are passed to the function call in a regular and recognizable function call or via a mechanism like call_user_func().

When defining a callback to work with that interface, your responsibility as a programmer is only to be sure that the function definition takes the correct number of parameters in the correct order, and with the correct names. The details of how it gets called are up to the mechanism that calls it.