$re = '/(Jan(?:uary)?|Feb(?:ruary)|Marc?h?|Apr[il1]?[I1l]?|May|June?|July?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:tober)?|Nov(?:ember)?|Dec(?:ember)?|20[01]\d)/';
$str = 'February 4 - March 23, 2015';
preg_match_all($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