<form id="myForm" action="insert.php" method="post">

        Name: <input type="text" name="name"/><br/>

        Username: <input type="text" name="username"/><br/>

        Password: <input type="password" name="password"/><br/>

        <button id="sub">Save</button>
</form>

    <span id="result"></span>

include_once('db.php');

$name = $_POST['name'];
$username = $_POST['username'];
$password = $_POST['password'];

if(mysql_query("INSERT INTO table_users VALUES('$name', '$username', '$password')")){
    echo "Successfully Inserted";
} else {
    echo "Insertion Failed";
}

$conn = mysql_connect('localhost', 'root', '');
$db = mysql_select_db('neverstoplearning');

<?php
$con = mysqli_connect("localhost","my_user","my_password","my_db");

// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }
?>