How to get parameters from a coded URL through get

How to get parameters from a coded URL through get
HTTP//Domain/?ID%3D3%26SERVER_ID%3DS1%26SIGN%3DF44F5AC51CBC95E13102CD5657082DC6

Want to $_get from this link to the three parameters of ID server_id and sign
How does the PHP file that receives the parameter need to process this link first?

Can you be a little more specific?
I'm a rookie, thank you. decoding URL PHP

------Solution--------------------
Reference:

reference: PHP code?12$str = "http://www.baidu.com/id%3D3%26server_id%3Ds1%26sign% 3df44f5ac51cbc95e13102cd5657082dc6 "; Echo UrlDecode ($STR);
Through $_get, it should be accessible.

The parameters to be obtained are dynamic, each time

...

$a = Explode (' & ', $QUERY _string);
$i = 0;
while ($i < count ($a)) {
    $b = Split (' = ', $a [$i]);
    Echo ' Value for parameter ', Htmlspecialchars (UrlDecode ($b [0])),
         ' Is ', Htmlspecialchars (UrlDecode ($b [1])), "
\ n ";
    $i + +;
}    

This is an example of a handbook.
------Solution--------------------
Var_dump (($_server[' Request_uri '));
Var_dump (($_server[' script_name '));
------Solution--------------------

$str = UrlDecode ($_server[' query_string ');
Parse_str ($str, $get);
Var_dump ($get [' sign ']);

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