On PHP, about using mysql or mysqli

Question

I'm running MySQL server version 5.0.77 on Linux (Rocks Cluster Distro), and I'm trying to connect to the same database with both MySQL and MySQLi PHP functions. The problem is that when the MySQLi code fragment is executed it does work, but the MySQL fragment doesn't (in case it matters; not even on separate PHP files).

As shown in the code below I'm attempting a connection to the same database on the same host, using the same user and password but the MySQL function version fails.

(If it helps I've already tried the same code on MySQL server 5.6.20 running in Windows with the same details ((local)host, database, user, password) and both functions work).

What might be the problem? Any help is appreciated.

The output and code fragment is the following:

Code:

<?PHP
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "tedDB";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("Error [mysqli]: ".$conn->connect_error);
} else {
    echo "Success [mysqli]";
}

echo "<br><br>";

$link = mysql_connect($servername, $username, $password)
    or die("Error [mysql_connect]: ".mysql_error());
echo "Success [mysql_connect]";
?>

Output (LINUX):

Success [mysqli]

Error: Access denied for user 'root'@'localhost' (using password: NO)

Output (Windows):

Success [mysqli]

Success [mysql_connect]