How to send data to an API call and get it back, using zillow.com API

I am trying to get the API from a website called zillow working for me, but I am way new to web stuff. They try and explain here how to use it, but it had me lost so I looked in their forums. Someone posted an "example" there, but I can not see where their code even calls the API. Basically I need to take a form field that will be an address and send that info to get data back, here is the source code taken from the guys example,

<html xml:lang="en" lang="en">
<head>
  <title></title>
</head>
<body>
<h3><font face="Verdana, Arial, Helvetica, sans-serif">Get Property < # >Zestimates 
  from Zillow</a></font></h3>
<form method="post" action="/Real-Estate/Zestimate.php" name="zip_search">
  <table align="center" width="618">
    <tr> 
      <td colspan="2"><font face="verdana, arial, sans-serif">Please specify the 
        Property address. </font></td>

      <td width="205" align="left"> <div align="left"><font face="Verdana, Arial, Helvetica, sans-serif"><#></a></font></div></td>
    </tr>
    <tr> 
      <td colspan="2"><font face="Verdana, Arial, Helvetica, sans-serif">Street</font>: 
        <input id="street2" type="text" maxlength="50" size="50" value="" name="street"/></td>
      <td>&nbsp;</td>
    </tr>
    <tr> 
      <td colspan="2"><font face="verdana, arial, sans-serif">City, State or ZipCode:</font> 
        <input id="citystatezip3" type="text" maxlength="50" size="20" value="" name="citystatezip"/></td>

      <td>&nbsp; </td>
    </tr>

  </table>
  <div align="center">
    <input name="submit" type="submit" value="Get Zestimate">
  </div>
</form>

You can see it is just a simple form that posts to itself right? But when I hit go it pulls the data from the API and displays it, but I do not see how. I would love any help you can offer, thank you!

Solution

Based on http://www.zillow.com/howto/api/APIFAQ.htm#devkit, there is no JavaScript API. Because of this (and cross-domain restrictions) you have to use a server-side language. I'll add a simple Java example.

EDIT: Okay, here goes. It just takes the street address and city/state, and returns a formatted value. Error-checking left out:

import java.text.NumberFormat;

import org.w3c.dom.*;
import org.xml.sax.*;

import javax.xml.parsers.*;

import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;

import java.io.*;

import java.util.Currency;

public class Zillow
{
    private static final DocumentBuilderFactory dbFac;
    private static final DocumentBuilder docBuilder;
    static
    {
        try
        {
            dbFac = DocumentBuilderFactory.newInstance();
            docBuilder = dbFac.newDocumentBuilder();
        }
        catch(ParserConfigurationException e)
        {
            throw new RuntimeException(e);
        }
    }
    private static final String DEEP_URL = "http://www.zillow.com/webservice/GetDeepSearchResults.htm";
    private static final String ZESTIMATE_URL = "http://www.zillow.com/webservice/GetZestimate.htm";

    private static final String ZWSID = ...;

    private static final NumberFormat nf = NumberFormat.getCurrencyInstance();

    // Returns Zestimate value for address.
    public static String getValuation(String address, String cityStateZip) throws SAXException, IOException
    {
        Document deepDoc = docBuilder.parse(DEEP_URL + 
                                        "?zws-id=" + ZWSID + 
                                        "&address=" + address + 
                                        "&citystatezip=" + cityStateZip);
        Element firstResult = (Element)deepDoc.getElementsByTagName("result").item(0);
        String zpid = firstResult.getElementsByTagName("zpid").item(0).getTextContent();
        Document valueDoc = docBuilder.parse(ZESTIMATE_URL + 
                                             "?zws-id=" + ZWSID + 
                                             "&zpid=" + zpid);
        Element zestimate = (Element)valueDoc.getElementsByTagName("zestimate").item(0);
        Element amount = (Element)zestimate.getElementsByTagName("amount").item(0);
        String currency = amount.getAttribute("currency");
        nf.setCurrency(Currency.getInstance(currency));
        return nf.format(Double.parseDouble(amount.getTextContent()));
    }

    public static void main(String[] args) throws Throwable
    {
        String address = args[0];
        String cityStateZip = args[1];
        System.out.println(getValuation(address, cityStateZip));
    }
}