=== table structure: ===

mysql> describe estado;
+-------------+-------------+------+-----+---------+----------------+
| Field       | Type        | Null | Key | Default | Extra          |
+-------------+-------------+------+-----+---------+----------------+
| id          | int(11)     | NO   | PRI | NULL    | auto_increment |
| descripcion | varchar(45) | YES  |     | NULL    |                |
+-------------+-------------+------+-----+---------+----------------+
2 rows in set (0.04 sec)


---------

=== file estado-create.php (fragment): ===

(...)
/ Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){

        $dsn = "mysql:host=$db_server;dbname=$db_name;charset=utf8mb4";
        $options = [
          PDO::ATTR_EMULATE_PREPARES   => false, // turn off emulation mode for "real" prepared statements
          PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION, //turn on errors in the form of exceptions
          PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC, //make the default fetch be an associative array
        ];
        try {
          $pdo = new PDO($dsn, $db_user, $db_password, $options);
        } catch (Exception $e) {
          error_log($e->getMessage());
          exit('Something weird happened'); //something a user can understand
        }

        $vars = parse_columns('estado', $_POST);
        $stmt = $pdo->prepare("INSERT INTO estado (descripcion) VALUES (?)");

        if($stmt->execute([ $descripcion  ])) {
                $stmt = null;
                header("location: estado-index.php");
            } else{
                echo "Something went wrong. Please try again later.";
            }

}
(...)


---------
=== inserting by hand: ===

mysql> INSERT INTO estado (descripcion) VALUES ("test1");
Query OK, 1 row affected (0.04 sec)