$re = '/,(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)/';
$str = '1234,"Calle Jaime III, 34", 67,3,U
1235,Avenida Los Algodones, 12,1,L
1236,"Calle Principal""31234", 46,3,H
1237,"Calle Alfonso X,22", 65,2,J';
preg_match_all($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