$re = '/((?<!Prof)(?<!Dr)(?<!Mr)(?<!Mrs)(?<!Ms))\./';
$str = 'Meanwhile Rector of Bogor Agricultural University, Prof. Dr. Herry Suhardiyanto, in his remarks about Mr. John requested that the graduate students should keep on studying and will finalize their studies on time. Present in that general audience were Mrs. Peterson of the Graduate School of Bogor Agricultural University, Dr.Dedi Jusadi, Secretary of the Graduate School for Doctoral Program of Bogor Agricultural University, Prof.Dr. Marimin.';
preg_match_all($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