$re = '/\("(?:[A-Z]|[a-z])[a-z]{3,}"\)/';
$str = '
words.Add("McLaren");//false
words.Add("Nissan");//true
words.Add("BMW");//false
words.Add("Subaru");//true
words.Add("Maserati");//true
words.Add("Mercedes Benz");//false
words.Add("Volkswagen");//true
words.Add("audi");//true
words.Add("Alfa Romeo");//false
words.Add("rollsRoyce");//false
words.Add("drive");//true';
$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