FYI, it was very easy to fix for PHP 7 (which broke it for me).
All I did was go to az-index-cache.php in the plugins folder and around line 956 I replaced
`$pos1 = ereg(‘:alnum:‘, $in1[‘initial’]);
$pos2 = ereg(‘:alnum:‘, $in2[‘initial’]);`
with
`$pos1 = preg_match(‘/:alnum:/’, $in1[‘initial’]);
$pos2 = preg_match(‘/:alnum:/’, $in2[‘initial’]);`
