PHP Novice Related issues! Ask your heroes to show you the maze!

PHP Novice Problem!! Ask your heroes to guide the maze!!
I got an open source project on the Internet. The only place where the registration verifies the username is a problem.
JS Call PHP file verification but do not know why the return of a 0 do not know there is a mistake.

JS Code:
function Chkname (form) {
if (form.name.value== "")
{
Name1.innerhtml= "Please enter your user name! ";
}
Else
{
var user = Form.name.value;

var url = "chkname.php?user=" +user;

Xmlhttp.open ("GET", url,true);
Xmlhttp.onreadystatechange = function ()
{

if (xmlhttp.readystate = = 4)
{
var msg = Xmlhttp.responsetext;
if (msg = = ' 2 ') {
Name1.innerhtml= "user name is occupied! ";
return false;
}else if (msg = = ' 1 ') {
Name1.innerhtml= "Congratulations, you can register!";
Form.c_name.value = "Yes";

}else{
Name1.innerhtml= "" +msg+ "";
}
}
}
Xmlhttp.send (NULL);
}
}

PHP Code: Session_Start ();
Include_once "conn/conn.php";
$reback = ' 0 ';
$sql = "SELECT * from Tb_user where name= '". $_get[' user ']. "'";
$rst = $conn->execute ($sql) or Die (' Execute error ');
if ($rst->recordcount () = = 0)
{

$reback = ' 1 ';
}
Else
{
$reback = ' 2 ';
}
Echo $reback;
?>


------Solution--------------------
discuss
$rst = $conn->execute ($sql) or Die (' Execute error ');
if ($rst->recordcount () = = 0)

------Solution--------------------
"PHP Ajax registered source code"
http://www.baidu.com/s?bs=php+ajax+%d7%a2%b2%e1%b5%c7%c2%bd%cd%cb%b3%f6+%d4%b4%c2%eb&f=8&rsv_bp=1& wd=php+ajax+%d7%a2%b2%e1+%d4%b4%c2%eb&inputt=190

