Как передать данные из input в базу данных?

<form method="post" action="/engine/ajax/module.php'>
    <input type="text" name="emailbuy" value="" placeholder="e-mailbuy">
    <button name="submit">Отправить</button>
</form>

<?php
if (isset($_POST['submit'])) {
$not_allow_symbol = array ("\x22", "\x60", "\t", '\n', '\r', "\n", "\r", '\\', ",", "/", "¬", "#", ";", ":", "~", "[", "]", "{", "}", ")", "(", "*", "^", "%", "$", "<", ">", "?", "!", '"', "'", " ", "&" );
$email = $db->safesql(trim( str_replace( $not_allow_symbol, '', strip_tags( stripslashes( $_POST['email'] ) ) ) ) );
$db->query( "INSERT INTO " . PREFIX . "_tableName (emailbuy) values ('".$email."')" );
}
?>