PHP and HTML form to update a mysql database

[careaa.fractal]

Hi. I have HTML form and i need php code when i want to subtract something from coulmn in mysql database.
Something like

http://www.daniweb.com/web-development/php/threads/101739/using-php-and-html-forms-to-update-a-mysql-database

MY FORM - HTML

<form action="objednat_potvrdenie.php" method="post">

Meno: <input type="text" name="meno"><br>
Priezvisko: <input type="text" name="prie"><br>
Mesto: <input type="text" name="mesto"><br>
Ulica: <input type="text" name="ulica"><br>
PSČ: <input type="text" name="psc"><br>
Počet kusov: <input type="text" name="p_k" id="p_k"><br>
Kód produktu: <input type="text" name="k_p" id="k_p"><br>

<input type="submit" value="Objednať">

</form> 

I want ask for sql, php, and demo pleaseee.

[Dani]

$link = new MySQLi(
    $server_name,
    $username,
    $password
);

if ($link->connect_error)
{
    die("Could not connect to $name database server: " . $link->connect_error);
}

if (!$link->select_db($db_name))
{
    die("Could not find $db_name database");
}

$link->real_query("DELETE FROM table WHERE row = 123");

Written from memory. Might have typos.