$re = '/^\S+(?=.*?Samsung_Galaxy_Note_2)/m';
$str = 'List of devices attached
192.168.56.101:5555 device product:vbox86p model:Samsung_Galaxy_Note_2___4_3___API_18___720x1280 device:vbox86p
192.168.56.102:5555 device product:vbox86tp model:Google_Nexus_7___4_3___API_18___800x1280 device:vbox86tp';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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