调用javascript函数，值在控制台中返回为undefined

Question

So I have a city dropdown which is populated by an onchange, I am trying to get it so that it doesn't require the onchange every time the page reloads, since it is a form.

this is the states dropdown, which works.

<p id=stateDiv><label>State</label></p><p><select name='States' id='States'  onchange='getCity(this.value)'>
            " . $states . "
        </select></p>";

this is the city drop down function call which does not work. I am new to javascript, so I am not sure about how to format a call with php.

if($state==""){   
echo '<p id="citydiv"></p>';
}else{
    echo '<p id="citydiv"><script type="text/javascript">getCity('.$state.');</script></p>';
}

getCity function

function getCity(stateId)
{
  var strURL="findcity.php?state="+stateId;
  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);
 }
}

Answer 1

When you get problems like this, ALWAYS look at the HTML source. In this case you might see:

getCity(GA);

Clearly this is wrong, that should be "GA" .

Whenever you dump a PHP variable into JavaScript, always use json_encode .

Answer 2

Along with what Kolink said, what does your javascript function "getCity" look like? If it is just returning a value, this will not work. You will either need to grab the element ( document.getElementById('cityDiv') ) and set the innerHTML to the return value OR use document.write instead of returning a value.