$loginUsername = "";
$loginPassword = "";
$password = '';

if(isset($_POST['username'])){
    $loginUsername = $_POST['username'];
}

if(isset($_POST['password'])){
    $loginPassword = $_POST['password'];
}


/*$loginUsername = $_POST["username"]; // declaro nombre de usuario
$loginPassword = $_POST["password"];*/

$request = "SELECT * FROM users where username='$loginUsername'";
$hash = $mysqli->query($request); // pido el hash de password

while($row = $hash->fetch_array()) {

    $password = $row["password"];
}

echo "<br>";
echo $password;
echo "<br>";