PHP Query String Limit

What browser are you using? HTTP 406 errors usually occur when the BROWSER does not like what the server sends. Does a completely different browser cause a 406 for exactly the same input?

There should also be some additional text with the error - an example would be

An appropriate representation of the requested resource /mysecript.php could not be found on this server.

Can you provide a screenshot of the failure?

The error is being returned by the server so don't think it's browser.
And the reason I think it's PHP and not Apache is because it works fine with an HTML file.

GET /test.php?phptestof129characterstring-NEW-WOVEN-FENCE-PANELS-GARDEN_W0QQitemZ200303392512QQihZ010QQcategoryZ139954QQtcZphotoQQcmdZViewItem
HTTP/1.1
Host: *****
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.5) Gecko/2008120122 Firefox/3.0.5
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-gb,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: agent_name=Tim

HTTP/1.1 406 Not Acceptable
Date: Tue, 03 Feb 2009 12:05:33 GMT
Server: Apache/2.2.3 (Red Hat)
X-Powered-By: PHP/5.1.6
Content-Length: 0
Connection: close
Content-Type: text/html

-----

GET /test.html?phptestof129characterstring-NEW-WOVEN-FENCE-PANELS-GARDEN_W0QQitemZ200303392512QQihZ010QQcategoryZ139954QQtcZphotoQQcmdZViewItem
HTTP/1.1
Host: *****
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.5) Gecko/2008120122 Firefox/3.0.5
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-gb,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: agent_name=Tim

HTTP/1.1 200 OK
Date: Tue, 03 Feb 2009 12:18:19 GMT
Server: Apache/2.2.3 (Red Hat)
Last-Modified: Fri, 19 Dec 2008 15:01:17 GMT
ETag: "156960d-221-94be8940"
Accept-Ranges: bytes
Content-Length: 545
Connection: close
Content-Type: text/html

have you tried compacting the QS?


function compressCrypt($string) {
        return base64_encode(gzcompress($string, 9));
}
 
function decompressCrypt($string) {
        return gzuncompress(base64_decode($string));
}

The query string is outside of my control, so it's not an option unfortunately.

Do you have PHP's mod_security enabled? If so, does the error persist if you disable it?