Hi,
Have you tried AQuA Wideband?
http://www.sevana.fi/voice_quality_testing_measurement_analysis.php
Charging by the technology presentation comparing audio is not a trivial task at all. Although this software does not intent to find audio similarity at first stage, it does compare files and provides percentage of their similarity. Besides it's multiplatform charging by the software and company blog: http://wordpress.sevana.fi
By using php it is possible please try this one
<?php
$audio1 = file_get_contents('audio1.wav');
$audio2 = file_get_contents('audio2.wav');
if($audio1 == $audio2)
echo "true";
else
echo "false";
?>