<?php
class Connection extends mysqli{
  //Connection data
  private $DB_NAME = "datos";
  private $DB_TABLE = "user";
  private $DB_HOST = "localhost";
  private $DB_PASSWORD = "password";
  private $DB_USER = "root";
  public $DB_CHARSET = "utf8";

  //Constructor
  public function __construct(){
    parent::__construct($this->DB_HOST,$this->DB_USER,$this->DB_PASSWORD,$this->DB_NAME);
    if ($this->connect_errno) echo "<div class='mensaje'>Error:
      {$this->connect_errno} -> {$this->connect_error}</div>";
    $this->set_charset($this->DB_CHARSET);
  }

  //Insert new record
  public function insert($id,$name,$password){
    $sql_comand = "INSERT INTO {$this->DB_TABLE} VALUES (?,?,?)";
    if(!($sentence = $this->prepare($sql_comand))){
      echo "Error(prepare): {$this->connect_errno} -> {$this->connect_error}";
    }
    $sentence = $this->bind_param("iss",$id,$name,$password);
    $sentence->execute();
    $sentence->close();
  }
  public function select(){
    $sql_comand = "SELECT * FROM {$DB_TABLE}";
    $querys = $this->query($sql_comand);
    while ($record = $querys->fetch_assoc()) {
      echo "ID: {$record['id']}";
      echo "name: {$record['name']}";
      echo "password: {$record['password']}";
    }
  }

}
?>

<form action="<?php htmlspecialchars($_SERVER['PHP_SELF']); ?>" method="post">
    <input type="number" class="id" name="id" maxlength="11" placeholder="ID"><br>
    <input type="text" name="name" maxlength="35" placeholder="Name"><br>
    <input type="password" name="password" maxlength="60" placeholder="Password"><br>
    <input type="submit" name="button" value="Submit">
</form>

<?php
  require "connection.php";

  if(isset($_POST["button"])){
    $con = new Connection();
    $id = htmlspecialchars($_POST["id"]);
    $name = htmlspecialchars($_POST["name"]);
    $password = htmlspecialchars($_POST["password"]);
    $con->insert($id,$name,$password);
    $con->close();
  }
?>