Stack Exchange
How to remove a specific parameter from the URL in PHP?
Example:
$url = http://example.com/?arg=val&arg2=test&arv3=testing&arv2=val2  
remove_url_arg($url, "arg2")
echo($url); // http://example.com/?arg=val&arv3=testing

The above remove_url_arg() function removes all occurrence of arg2 argument from the URL 

unset($_GET['arg2']);
$query_string = http_build_query($_GET);

if it's not on request but to parse whole url
$parsed = parse_url($url);
$qs_arr = parse_str($parsed['query'],1);
unset($qs_arr['arg2']);
$parsed['query'] = http_build_query($qs_arr);

and then assemble the url back.
or one-liner regexp
