$re = '/(\d+x\s+((?!\dx\s).+))/i';
$str = '1x ACOUCH 90X200 NICE GRAY (3 colli) 1x matras 85x205x12 2x matras 80x190x11 Some specs 14x Premium otherproduct 90x200x23 HR34';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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