This is a simple tutorial on how to get a dropdown list value using simple ajax and php
Create a html page named country.html and add the below codes,
HTML CODE

<select name="country" onChange="getCurrencyCode('find_ccode.php?country='+this.value)">
 <option value="">Select Country</option>
        <option value="1">USA</option>
        <option value="2">India</option>
        <option value="3">Uk</option>
</select>
<input type="text" name="cur_code" id="cur_code" />

Javascript CODE

function getCurrencyCode(strURL)
{
  var req = getXMLHTTP();
  if (req)
  {
        //function to be called when state is changed
        req.onreadystatechange = function()
        {
          //when state is completed i.e 4
          if (req.readyState == 4)
          {
                // only if http status is "OK"
                if (req.status == 200)
                {
                        document.getElementById('cur_code').value=req.responseText;
                }
                else
                {
                        alert("There was a problem while using XMLHTTP:\n" + req.statusText);
                }
          }
        }
        req.open("GET", strURL, true);
        req.send(null);
  }
}

Now create a PHP file named code.php and add the below codes,

< ?php
$country=$_REQUEST&#91;'country'&#93;;
switch($country)
{
        case "1" :
                echo "USD";
                break;
        case "2" :
                echo "Rupees";
                break;
        case "3" :
                echo "Pound";
                break;
}
?>

THATS IT!!!!!!!!!!!!!!!!

As you can see its pretty simple to understand this tutorial.

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