add_query_arg() does not return Strict XHTML links.

[majelbstoat]

add_query_arg() is a useful general purpose function that can be employed to extend a query string if it already exists. However, the appending of new variables is done with '&' rather than '&', which means that links returned are not XHTML Strict 1.0 or XHTML 1.1 compliant. This is not important for wp-admin pages, but causes problems on site pages. Parsing errors in Firefox and possible more browsers cause the site not to be visible, returning only an XML error. The following patch alters add_query_arg() to append using the correct '&' connector, which would greatly enhance its usability for plugins that wish to work with links.

add & instead of &

An alternative solution would be to add a 'strict = false' final argument which would determine whether to output & or &. This might necessitate a refactoring of the argument handling code at the top.

+1

XHTML validity is one of WordPress' big things. Don't have time to give this a thorough look now, but I'll return to it.

Might break if we use it in HTTP, for example. I recommend adding a parameter which is on by default.

Or leave it alone and run the output through urlencode() if so needed.

I assume you mean htmlentities ;)

er, yeah.

Yeah, that's what I ended up doing.

And will using & break HTML?

No, that's not what I said. It will break if used in HTTP headers sent with a header() call.

Yes we should do this on a different level, so we don't break redirects.