Manual:Hooks/LinkBegin

Details
Return false to skip default processing and return $ret. See documentation for Linker::link for details on the expected meanings of parameters.
 * $skin: the Skin object
 * $target: the Title that the link is pointing to
 * &$text: the contents that the  tag should have (raw HTML); null means "default"
 * &$customAttribs: the HTML attributes that the  tag should have, in associative array form, with keys and values unescaped. Should be merged with default values, with a value of false meaning to suppress the attribute.
 * &$query: the query string to add to the generated URL (the bit after the "?"), in associative array form, with keys and values unescaped.
 * &$options: the options. Can include 'known', 'broken', 'noclasses'.
 * &$ret: the value to return if your hook returns false.