$re = '/(benz\s+[[:alpha:]]+)\d\w*/m';
$str = '2010 mercedes-benz sl500r
2010 mercedes-benz e550
2010 mercedes-benz glk350
2010 mercedes-benz c300w
2010 mercedes-benz 300
("2010 mercedes-benz sl",
"2020 mercedes-benz e",
"2017 mercedes-benz glk",
"2013 mercedes-benz c",
"2014 mercedes-benz 300")';
$subst = "\1";
$result = preg_replace($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