Is it possible to convert to a WAV file to AIFF in PHP, and viceversa?

I know it's possible to covert from AIFF and WAV to MP3, but in my project I need to have available all three formats (AIFF, WAV and MP3) from AIFF and WAV inputs. Is it possible?

<?php
    exec("ffmpeg -i file.wav -f aiff -ab 128000 -ar 44100 file.aif");
?>