title: While submitting the form, it throws an error
body: <p>**it throws an error  </p>
  
  <blockquote>
    <p>Undefined offset: 0 in C:\xampp\htdocs\test_login\add_data.php on line 10</p>
  </blockquote>
  
  <p>line 10 has  $_SERVER["REQUEST_METHOD" == "POST"]**</p>
  
  <pre><code>&lt;?php 
  require_once 'mysql_connect.php';
  
  if ($_SERVER["REQUEST_METHOD" == "POST"]) {
      if (empty($_POST['username'])) {
          echo "Username required.";
      }else{
      $username = handle_data($_POST['username']);
      }
  
      if (empty($_POST['password'])) {
          echo "Password required.";
      }
      else{
      $password = handle_data($_POST['password']);
      }
  
      if ($_POST['cpassword'] != $_POST['password']) {
          echo "Passwords donot match!";
      }
  
      if (!is_numeric($_POST['age'])) {
          echo "Age must be a number.";
      }
  
  
  $query = "INSERT INTO students(username, password, age) VALUES(?, ?, ?)";
  $stmt = mysql_stmt_prepare($conn, $query);
  if ($stmt) {
      mysqli_stmt_bind_param($stmt, 'ssi', $username, $password, $age );
      mysqli_execute($stmt);
      echo "Registration Made!";
      mysqli_stmt_close($stmt);
      mysqli_close($conn);
  }
  
  }
  
  function handle_data($data){
  $data = trim($data);
  $data = stripcslashes($data);
  $data = htmlspecialchars($data);
  return $data;
  }
  
  ?&gt;
  </code></pre>
  
  <p>What is the actual error it is pointing at??</p>