$re = '/(?<=select\s)[a-zA-Z,\s__.]+(?=from)/mi';
$str = 'SELECT account.name.account,name,website,name__C (SELECT id,name from contact),(SELECT id,name from sales), from accounts';
preg_match_all($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