$re = '/(?:\s+?).+?\s+(S\/\d+)\s+(\d+)\s+(S\/\d+\.\d+)/m';
$str = 'Detalle\\n Unidad\\n Cantidad\\n Total\\n Triple Insomnio Especial S/37 1 S/37.90 Insomnio Especial S/21 2 S/23.12 *Tipo de papa:* - Papa Amarilla Tumbay S/0.00\\n *Adicional :* - Quesp cheddar S/0.00\\n *Agrega Bebida:* - Fanta 400 ml S/0.00\\n *Salsas:* - Mayonesa S/0.00\\n - Ketchup S/0.00\\n - Golf S/0.00\\n - Guacamole S/0.00\\n - Ají S/0.00\\n - Tártara S/0.00\\n - Mayo-aji S/0.00\\n ';
preg_match_all($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