<?php

$dbhost = "SOMETHING";
$dbname = "ZIP";
$dbusername = "SOMETHING";
$dbpassword = "SOMETHING";

$link = new PDO("mysql:host=$dbhost;dbname=$dbname",$dbusername,$dbpassword);


$zip = htmlspecialchars($_POST['zip']);

$statement = $link->prepare("INSERT INTO ZIP(ZIP)
    VALUES(:zip)");

$statement->bindParam(':zip', $zip);
$statement->execute();

?>