不知道问题出在哪里..但是数据没有出现在数据库中..
if(isset($_POST['sign up']))
{
$name=$_REQUEST['username'];
$password=$_REQUEST['password'];
$fname=$_REQUEST['fname'];
$lname=$_REQUEST['lname'];
$email=$_REQUEST['email'];
mysql_query("insert into sign_up ('username','password','fname','lname','email') VALUES('$name' , md5('$password') , '$fname' , '$lname','$email'");
}