$re = '/(?:(\d{1,2})(?:th|nd|rd).* ([a-z]{3})[a-z]*|([a-z]{3})[a-z]* (\d{1,2})),\s*(\d{4})/i';
$str = 'this amendment of lease, made and entered as of the 10th day of august, 2016, by and between john doe and jane smith
this agreement, made and entered as of May 1, 2016, between john doe and jane smith';
preg_match_all($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