Details

This is an associative array where the key is an extension-defined tag (typically the extension name), and the value is a PHP callback. These will be called as an OutputPageParserOutput hook, if the relevant tag has been registered with the parser output object.

Registration is done with

$pout->addOutputHook( $tag, $data );

The callback has the form:

function outputHook( $outputPage, $parserOutput, $data ) { 
  /*...*/
}