GET变量的PHP值是0？

Question

I am having problems creating a simple PHP script. The $_GET["give"] variable is always 0 in PHP, but I did define it in the URL. If it's not defined, my script redirects.

    if (isset($_GET["give"])&&$_GET["give"]!="") {
        echo "give GET detected<br />";
        $user = $_GET["give"];
        echo $_GET["give"]+$user+"<br />";
    }
    header("Location: /diamonds/"); //this document, but removing arguments.

The URL is fine, /?give=kroltan, it should echo kroltan. But instead, I get this in the browser:

   give GET detected <br>
   0

It doesn't even echo the $user variable, although it's the same value as $_GET["give"]. And no <br> after that too

Answer 1

This is PHP. You concat strings with a . and not a +.

As @MarcB said in the comments - in other words, you're doing a mathematical addition on strings, so PHP is converting your kroltan string to a 0.

String operators in PHP