File generation in PHP

It's a 10-minutes job if you master the PHP language. ------------------------------- We have on our website a PHP file that generate a TXT file. This generated TXT file contains the inside of a big drop-down list : <option value="1-Player">1-Player </option> <option value="2-Player (Alternatively)">2-Player (Alternatively) </option> <option value="2-Player (Simultaneous)">2-Player (Simultaneous) </option> Etc... Portion of the actual code is : foreach ($listeunique as $valeur) { $a_ecrire = "<option value=\"".$valeur."\">"; $a_ecrire.= htmlspecialchars($valeur)." "; $a_ecrire.= "</option>"; fwrite($ouverture, $a_ecrire, 4096); } fclose($ouverture); unset($ouverture, $a_ecrire); ------------------------------------ Some values in this list are presented like this : <option value="AOF/Eiji">AOF/Eiji </option> <option value="AOF/Jack">AOF/Jack </option> <option value="AOF/Jin">AOF/Jin </option> Etc... What's we want is the PHP file should generate something like this automatically : <optgroup label="AOF"> <option value="AOF/Eiji">Eiji</option> <option value="AOF/Jack">Jack</option> <option value="AOF/Jin">Jin </option> </optgroup> Everything before the / should appears as an <optgroup> automatically done by the PHP file. And this <optgroup> should close at the good place for each family. There are many cases: <option value="Aircrafts/Lockheed">Aircrafts/Lockheed </option> <option value="Aircrafts/McDonnell">Aircrafts/McDonnell</option> ....... <option value="Animals/Bears">Animals/Bears </option> <option value="Animals/Birds">Animals/Birds </option> <option value="Animals/Cats">Animals/Cats </option> ...... Etc...