$re = '/([^\\\\]+)\\\\(\S+)\s([^\\\\]+)\\\\([^\\\\]+)\\\\(.+)/m';
$str = 'Projects\\UP/PS (21063)\\2789 (spain) / Ref/15\\Email
casi, serían 1=Projects (pero es tan facil que lo he obviado), 2=UP/PS, 3=(21063), 4=2789 (spain) / Ref/15, 5=Email';
preg_match_all($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