<?php
$firstname = "";
$middlename = "";
$lastname = "";
$username = "";
$password = "";
include("conn.php");
if (isset($_POST['firstname']))
{
$firstname= $_POST['firstname'];
$middlename= $_POST['middlename'];
$lastname= $_POST['lastname'];
$username= $_POST['username'];
$password= $_POST['password'];

$sql= 'INSERT INTO tbl_jhaiyem (firstname, middlename, lastname, username, password) VALUES("'.$firstname. '","'.$middlename. '","'.$lastname. '","'.$username. '","'.$password. '");

if(mysqli_query($conn,$sql))
echo "Successfully Added!";
else
echo "An error occured while trying to add the record.";

}
?>
<form method="post" action="submit.php">
Firstname: <input type="text" name="firstname"