$re = '/(?=.*?[a-z])(?=.*?\')[a-z\']+/mi';
$str = '\'word\'
\'Word
\'W\'ord
\'W\'or\'d
Word\'
w\'orD
w\'o\'r\'d
word';
preg_match_all($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