I solve the problem.
I used the PDO instead mysqli.
This is my code:
<?php
$servername = "localhost";
$my_username = "";
$my_password = "";
$dbname = "";
try {
$conn = new PDO("mysql:host=$servername;dbname=$dbname", $my_username, $my_password);
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$conn->exec("SET NAMES utf8");
$id=$_POST['id'];
$username=$_POST['username'];
$password=$_POST['password'];
$stmt = $conn->prepare("INSERT INTO users_account VALUES ('".$id."','".$username."', '".$password."')");
$stmt->bindParam(':id', $id);
$stmt->bindParam(':username', $username);
$stmt->bindParam('
assword', $password);
$stmt->execute();
echo "ok";
} catch(PDOException $e) {
echo "Error: " . $e->getMessage();
}
$conn = null;
?>