$re = '/(?<inner>(?<![\p{L}\'])(?:\p{L}+\')+\p{L}+(?![\p{L}\']))|
(?<began>(?<!\p{L})(?:\'\p{L}+)+(?![\p{L}\']))|
(?<ended>(?<![\p{L}\'])(?:\p{L}+\')+(?!\p{L}))|
(?<outer>(?<!\p{L})\'\p{L}+\'(?!\p{L}))/mix';
$str = '\'Twas---Wha\'? Wouldn\'tcha\'? \'Twas, or \'twasn\'t, \'tis what\'s \'tween dawn \'n\' dusk \'n stuff. Cookin\'? \'Sams\' place, \'yo\'';
preg_match_all($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