Create different cached versions for every different browser

[jerry9]

I would like to use a custom salt that creates a new cache for every different browser. According to the example described in the quick cache options page, in order to achieve a new cache for every browser I should enter $_SERVER["HTTP_USER_AGENT"] into the md5 salt field. When I try entering the code on my website I am told "Your MD5 Version Salt may contain syntax errors" and as a result I do not get a different cache for each browser. Any suggestion?

Thanks.

[newcomer]

I use $_SERVER['HTTP_USER_AGENT'] and no error

May be you can use : empty($_SERVER['HTTP_USER_AGENT'])?'none':$_SERVER['HTTP_USER_AGENT']