how I get city id from a php page
<p>I am creating a registration form for my web site. In my registration form, there are two select boxes to select user's district and there city. So I need to do it, when a user select their district then automatically display city select box with cities which relevant to above selected district. To do this I used Ajax and php. I used findcity.php page to display the city in my register.php page. My problem is when I am try to get city id from the register.php page I cant get it. It I need to get to send with other data from register.php page to database. 
Please anybody help me to do it.
and suggestions are greatly appreciated. 
thank you. </p>

<p>from my register.php page </p>

<pre><code>&lt;div&gt;
&lt;label for="district"&gt;District &lt;img src="../images/required_star.png" alt="required" /&gt; : &lt;/label&gt;
&lt;?php

    require_once ('../includes/config.inc.php');    
    require_once( MYSQL2 );

    $query="select * from district order by district_id";
    $result = mysqli_query( $dbc, $query);

        echo '&lt;select name="district" class="text" onChange="getCity(' . "'" . 'findcity.php?district=' . "'" . '+this.value)"&gt;';
        echo '&lt;option value=""&gt;-- Select District --&lt;/option&gt;';

        while( $row = mysqli_fetch_array($result, MYSQLI_NUM)) { 
            echo '&lt;option value="' . $row[0] . '"';

            // Check for stickyness: 
            if ( isset( $_POST['district']) &amp;&amp; ( $_POST['district'] == $row[0] ))    
                echo ' selected="selected"';

                echo " &gt;$row[1]&lt;/option&gt;";    
        }
        echo '&lt;/select&gt;';
?&gt; 

&lt;/div&gt;    
&lt;div&gt;
    &lt;label for="city"&gt;City &lt;img src="../images/required_star.png" alt="required" /&gt; : &lt;/label&gt;
    &lt;input type="hidden" name="reg_locationid" id="reg_locationid" value="56" /&gt;
    &lt;div id="citydiv" style="position: relative; top: -14px; left: 130px; margin-bottom: -26px;"&gt;
        &lt;select name="city" class="text"&gt;
            &lt;option&gt;-- Select City --&lt;/option&gt;
        &lt;/select&gt;
    &lt;/div&gt;
&lt;/div&gt;
</code></pre>

<p>this is findcity.php page </p>

<pre><code>&lt;?php

$districtId=$_GET['district'];

require_once ('../includes/configaration.inc.php'); 
require_once( MYSQLCONNECTION );

$query="select city_id, city_name from city2 where district_id=$districtId";
$result=mysqli_query( $dbc, $query);



echo '&lt;select name="city" class="text"&gt;
        &lt;option&gt;-- Select City --&lt;/option&gt;';

while($row=mysqli_fetch_array($result, MYSQLI_NUM)) { 

    echo '&lt;option value="' . $row[0] . '"';

    // Check for stickyness: 
    if ( isset( $_POST['city']) &amp;&amp; ( $_POST['city'] == $row[0] )) { 
        echo ' selected="selected"';

        //echo '&lt;input type="hidden" name="city"  value="' . $row[0] . '"'; 

    }
        echo " &gt;$row[1]&lt;/option&gt;";  

}

echo '&lt;/select&gt;';
</code></pre>

<p>?></p>

<p>this is my ajax functions </p>

<pre><code>function getXMLHTTP() { //fuction to return the xml http object
    var xmlhttp=false;  
    try{
        xmlhttp=new XMLHttpRequest();
    }
    catch(e)    {       
        try{            
            xmlhttp= new ActiveXObject("Microsoft.XMLHTTP");
        }
        catch(e){
            try{
            xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
            }
            catch(e1){
                xmlhttp=false;
            }
        }
    }

    return xmlhttp;
}



function getCity(strURL) {      

    var req = getXMLHTTP();

    if (req) {

        req.onreadystatechange = function() {
            if (req.readyState == 4) {
                // only if "OK"
                if (req.status == 200) {                        
                    document.getElementById('citydiv').innerHTML=req.responseText;                      
                } else {
                    alert("There was a problem while using XMLHTTP:\n" + req.statusText);
                }
            }               
        }           
        req.open("GET", strURL, true);
        req.send(null);
    }

}
</code></pre>
