网站验证与PHP无法正常工作？

I am having trouble trying too check theses two inputs uname and passwod. I can get one to work on its own but I keep getting an error when I try to pass them both back up.

<?php 
// define variables and set to empty values
$usernameErr="";
$passwordErr="";
$username= "";
$password="";

if ($_SERVER["REQUEST_METHOD"] == "POST")
{

    if (empty($_POST["uname"]))
        {
         $usernameErr = " username is required <br>";
         print $usernameErr;
        }

    else
        {
        $username = checkUserData($username);
        }   


    if (empty($_POST["passwd"]))
        {
         $passwordErr = "  password is required <br>";
         print $passwordErr;
        }

    else
        {
        $password = checkUserData($password);
        }   
    }

Here is were the problem is. I am passing down to check the data to stop attacks. I have tried multiple ways of joining them together but everything has failed.

function checkUserData($username)
{
    $username = htmlspecialchars($username);
    $username = trim($username);
    $username = stripslashes($username);
    return $username;
}

function checkUserData($password)
{
    $password = htmlspecialchars($password);
    $password = trim($password);
    $password = stripslashes($password);
    return $password;
}

I'm printing just to check it's working.

print ("welcome " .checkUserData($_POST["uname"]));
print ("welcome " .checkUserData($_POST["passwd"]));
?>

Any help would be great.

Both functions are doing the same thing so generalise them

function SanitizeData($var)
{
    $var= htmlspecialchars($var);
    $var= trim($var);
    $var= stripslashes($var);
    return $var;
}

Now in your checking process call

$username = SanitizeData($_POST["uname"]);

Or

$password = SanitizeData($_POST["passwd"]);

Although this sanitization is unnecessary at best and destructive at worst if you are going to use these fields in a query, it would be better to use a parameterized query and the PDO database extension.