$re = '/(.*?)
(?<=[.!?]|[.!?][\'"])
(?<!
Mr\.|
Mrs\.|
Ms\.|
Jr\.|
Dr\.|
Prof\.|
Sr\.|
Ltd\.|
\s[A-Z]\.)
\s+
/ixD';
$str = 'Start Date. Test. Test||. Test';
preg_match_all($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