$re = '/[^"]$/m';
$str = '1,A,"apple"
2,B,"banana"
3,C,"cherry
4,D,"durian"
5,E,"elderberry
6,F,"Fanta™"
7,G,"grape
8,H,"honeydew"';
$subst = "$0\"";
$result = preg_replace($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