This is the JavaScript and PHP code that powers the iTunes Artwork Finder available at https://bendodson.com/projects/itunes-artwork-finder/
To use on your own site, simply upload both the JavaScript and PHP files and then initialise the script with something like:
<div>
<form action="" method="get" accept-charset="utf-8" id="iTunesSearch">
<select name="entity" id="entity">
<option value="tvSeason">TV Show</option>
<option value="movie">Movie</option>
<option value="ebook">iBook</option>
<option value="album">Album</option>
<option value="software">App (iPhone or Universal)</option>
<option value="iPadSoftware">App (iPad)</option>
<option value="macSoftware">App (macOS)</option>
<option value="audiobook">Audiobook</option>
<option value="podcast">Podcast</option>
<option value="musicVideo">Music Video (may not work)</option>
<option value="id">Apple ID (Movie)</option>
<option value="idAlbum">Apple ID (Album)</option>
<option value="shortFilm">Short Film</option>
</select>
<input type="text" class="text" name="query" id="query" />
<select name="country" id="country">
<option value='us'>United States of America</option>
<option value='gb'>United Kingdom</option>
</select>
<input type="submit" class="submit" value="Get the artwork" />
</form>
</div>
<div id="results">
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="itunes.js"></script>
You will need to amend the first line within itunes.js so that the pathToAPI variable points to the absolute URL of the api.php file running on a PHP server.