WikiPage::newFromID( 0 ) actually queries the 'page' DB table to look up article ID 0. But MW code assumes that page_id == 0 means the page does not exist, e.g. Title sets mArticleId to 0 if article not found. So newFromID() could return null early if ( $id == 0 ).

One caller of this is ApiBase::getTitleOrPageId() , as a result API clients that pass pageid=0 hit the database, some even querying 'fromdbmaster'. AFTv5 is one example (bug 61164).

Version: 1.23.0
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=61164