This is not really an IMDB API. There doesn't seem to be a way to use IMDB API for free anyway. However this API does returns movies, is free and has database big enough for most cases.
Finding movies or tv shows from PHP using free API:
$title = 'Coherence';
$data = json_decode(file_get_contents('http://api.rest7.com/v1/movie_info.php?title=' . $title));
if (@$data->success !== 1)