.htaccess url encoded string not passing to page correctly

Question

I have a rewrite rule in .htaccess

RewriteRule ^page/(.*)$ my-php-page.php?cid=$1

I am passing a encoded string which contains characters like = and + - this is the encoded string;

V1ihnKpip6WpnY7Wm5zn2+6YUtLf2KCh4eKY

When in the complete URL it's

http://www.example.com/my-php-page.php?cid=V1ihnKpip6WpnY7Wm5zn2+6YUtLf2KCh4eKY

now this doesn't work because of the + sign. So I want to send the cid urlencoded which then becomes;

http://www.example.com/my-php-page.php?cid=V1ihnKpip6WpnY7Wm5zn2%2B6YUtLf2KCh4eKY

The + sign becomes %2B. This works great, except when I try this through the RewriteRule in .htaccess - it doesn't work. So the URL would be

http://www.example.com/page/V1ihnKpip6WpnY7Wm5zn2%2B6YUtLf2KCh4eKY

The mypage.php file actually receives the cid as V1ihnKpip6WpnY7Wm5zn2 6YUtLf2KCh4eKY for some reason replacing %2B with a blank space.

Any ideas why it may be doing that? And how can I fix it. Many thanks for the help.

EDIT

I just found this solution - PHP $_GET var with urlencode and "&" bug - but I was wondering if there was a more elegant solution in .htaccess than having to urlencode the string twice?

Answer 1

Try adding the B rewrite flag. This flag tells mod_rewrite to escape backreferences, the documentation says this:

_rewrite has to unescape URLs before mapping them, so backreferences will be unescaped at the time they are applied. Using the B flag, non-alphanumeric characters in backreferences will be escaped.

Since the % character is reserved for backreferences to groupings matched in RewriteCond statements preceeding the RewriteRule, mod_rewrite treats them differently and could end up attempting to replace the %2 with a blank backreference.

So your rule should look like this:

RewriteRule ^page/(.*)$ my-php-page.php?cid=$1 [B]