[PHP] Function Problem

I'm having a bit of trouble getting my script to work, i've had it working before, so i feel like this is a stupid problem, but I can't figure out what I'm doing wrong.

Code:

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Fatal error:  Cannot redeclare login() (previously declared in /home/public_html/includes/functions.php:22) in /home/public_html/includes/functions.php on line 44

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That's the error im getting for this script:

PHP Code:

---

<?    
    //Require the database connection
    require_once("header.php");    
    
    function login()
    {


  
                //Define variables 
                $username = $_POST['username'];
                $password = sha1($_POST['password']); // Encrypts the password.
                $q = mysql_query("SELECT * FROM `users` WHERE username = '$username' AND password = '$password'");
                if($q)
                    {
                        $check = mysql_num_rows($q);
                    }
                        if($check == 1)
                            {
                                while ($row = mysql_fetch_assoc($q))
                                    {
                                        $_SESSION['id'] = $row['ID'];
                                        $_SESSION['loggedin'] = true;
                                        $_SESSION['username'] = $username;
                                        $_SESSION['password'] = $password;
                                        Header("Location: index.php");
                                    }            
                            }
                else
                    {
                        die("Wrong username or password");
                    }
    }
?>

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Any solutions? It's probably a minor fix, but I can't figure it out for the life of me.

Is that your functions.php?
Does header.php have a login function?
Just to be safe, do any other files have the login functon?

You already made a function named 'login()'. Therefor you cannot make it again. So either rename the second function or delete it / merge both functions together.

Lucky for you I have experience with that in PHP working with multiple modules and such and duplicate functions came up sometimes.

Try this,

PHP Code:

---

if(!function_exists(login))
{
function login()
    {


  
                //Define variables 
                $username = $_POST['username'];
                $password = sha1($_POST['password']); // Encrypts the password.
                $q = mysql_query("SELECT * FROM `users` WHERE username = '$username' AND password = '$password'");
                if($q)
                    {
                        $check = mysql_num_rows($q);
                    }
                        if($check == 1)
                            {
                                while ($row = mysql_fetch_assoc($q))
                                    {
                                        $_SESSION['id'] = $row['ID'];
                                        $_SESSION['loggedin'] = true;
                                        $_SESSION['username'] = $username;
                                        $_SESSION['password'] = $password;
                                        Header("Location: index.php");
                                    }            
                            }
                else
                    {
                        die("Wrong username or password");
                    }
    }
} 


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function_exists() is a life-saver!

:o, didn't knew that one existed lol :P