How to add manual contact form in a page?

I want to have a page where a user can insert their contact form (name, address, city, zip, email etc.). Their info will be stored in MyPhpAdmin database in a table. Is it possible to do it within wordpress template? I have a template specifically called template-join-us.php for this.

I inserted these codes in the template right after the if (have_post()) loop:

<? if ( $_POST['email'] ) { ?>

<center>Thank you. You will be receiving a confirmation e-mail shortly.</center>

<? } else { ?>
<form action="index.php?page_id=4" method="post"> --> this is the location of submission
    Name: <input type="text" name="name" /><br />
    Address: <input type="text" name="address" /><br />
    City: <input type="text" name="city" /><br />
    State: <input type="text" name="state" /><br />
    Zip: <input type="text" name="zip" /><br />
    Email: <input type="text" name="email" /><br />
    Phone: <input type="text" name="phone" /><br />
    <br />
    <input type="submit" name="submit" value="submit" />
    </form>
<? } ?>

<? if ( $_POST['email'] ) {
    include_once("db.php"); --> to call localhost database to insert the contact form data

$query  = "INSERT INTO contact_form (<code>name</code>, <code>address</code>, <code>city</code>, <code>state</code>, <code>zip</code>, <code>email</code>, <code>phone</code>, <code>stamp</code>) VALUES ('".$_POST['name']."', '".$_POST['address']."', '".$_POST['city']."', '".$_POST['state']."', '".$_POST['zip']."', '".$_POST['email']."', '".$_POST['phone']."', NOW() )";

$result = mysql_query($queryb) or die("Query Error: ".mysql_error());

$emailsend = strval($_POST['email']);

Code below is to change sender's email address to string so that the confirmation email will also be sent to sender's email as seen below

if ( $result ) { mail( '[email protected]' , 'Insert Header Topic Here' , 'Insert Email Content Here', 'From: [email protected]' . "\r\n" .

    'Reply-To: webmaster@myself' . "\r\n" .
    'X-Mailer: PHP/' . phpversion());
	}
mysql_close($db);
}
?>

I tried this code then did a test submission, then the page just gives a blank result with warning: “Sorry, no posts matched your criteria.”

What’s wrong? How to fix it?