$re = '/-(?:[AR](?:-(?:OK|NG))?|W|C)$/m';
$str = 'Word1-A-OK
Word2-Sample-R-OK
Word3-A
Word1-R
Word2-Sample-A-NG
Word3-R-NG
Word1-W
Word2-Sample-C';
$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