基本的php/db密码加密

我已经为android应用程序的登录/注册功能设置了两个简单的PHP文件。

我想知道一个简单的方法，让它保存/写一个加密的密码到mysql数据库。目前只能用明文作为密码。

register.php的代码为:

$username = $_POST["username"];
$email = $_POST["email"];
$password = $_POST["password"];

$statement = mysqli_prepare($con, "INSERT INTO User (username, email, password) VALUES (?, ?, ?)" );
mysqli_stmt_bind_param($statement, "sss", $username, $email, $password);
mysqli_stmt_execute($statement);
mysqli_stmt_close($statement);
mysqli_close($con);

和登录的代码是:

$password = $_POST["password"];
$username = $_POST["username"];
$statement = mysqli_prepare($con, "SELECT * FROM User WHERE username = ? AND password = ?");
mysqli_stmt_bind_param($statement, "ss", $username, $password);
mysqli_stmt_execute($statement);
mysqli_stmt_store_result($statement);
mysqli_stmt_bind_result($statement, $userID, $username, $email, $password);
$user = array();
while(mysqli_stmt_fetch($statement)) {
    $user[username] = $username;
    $user[email] = $email;
    $user[password] = $password;
}
echo json_encode($user);
mysqli_stmt_close($statement);
mysqli_close($con);

很简单的问题，我知道，但只是学习自己。由于

基于Jamesking56的链接/响应，我得出了这个，但现在它根本没有写到db:

$username = $_POST["username"];
$email = $_POST["email"];
$password = $_POST["password"];
$passwordHash = password_hash($password, PASSWORD_DEFAULT);
$statement = mysqli_prepare($con, "INSERT INTO User (username, email, password) VALUES (?, ?, ?)" );
mysqli_stmt_bind_param($statement, "sss", $username, $email, $passwordHash);
mysqli_stmt_execute($statement);
mysqli_stmt_close($statement);
mysqli_close($con);