$re = '/^.*\bAC=([^,]+)/m';
$str = '"AB=ikkw0116,AC=BE D Work stations,AC=BE D stations,AC=D Allocated,AD=pnser,AD=pnsas,AD=owned,AD=increased"
"AB=ikkWA001S1,AC=BE D HD,AC=D Allocated,AD=pnser,AD=pnsas,AD=owned,AD=increased"
"AB=iksw0084,AC=Domain View,AD=pnsas,AD=owned,AD=increased"
"AB=GHRS05900263,AC=Big stations,AC=GHR,AC=BE,AD=ger,AD=eu,AD=intra"';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php