why this Javascript function doesn't work?
<p>I use the following javascript function,</p>

<pre><code>function get_check_value(formId,checkboxId,TxtboxId)
{
alert(formId);

var c_value = "";
for (var i=0; i &lt; document.formId.checkboxId.length; i++)
   {
   if (document.formId.checkboxId[i].checked)
      {
      c_value = c_value + document.formId.checkboxId[i].value + "\n";
      }
   }
   alert(c_value);
   document.getElementById(TxtboxId).value= c_value;
  // alert(c_value.value);
</code></pre>

<p>}</p>

<p>and my php page has this,</p>

<pre><code>&lt;form name="orderform" id="orderform"&gt;
&lt;input type="text" name="chId" id="chId" &gt;
    &lt;table align="center" border="0"&gt;
        &lt;tr&gt;
            &lt;td&gt;Country&lt;/td&gt;
        &lt;/tr&gt;
    &lt;? foreach($country as $row){   ?&gt;
    &lt;tr&gt;
    &lt;td&gt;&lt;?= $row['dbCountry']; ?&gt;&lt;/td&gt;
    &lt;td&gt;&lt;input type="checkbox" name="CountrycheckId" id="CountrycheckId" value="&lt;?= $row['dbCountryId']; ?&gt; " onClick="get_check_value('orderform','CountrycheckId','chId')"&gt;&lt;/td&gt;  
    &lt;? }  ?&gt;
    &lt;/tr&gt;
    &lt;/table&gt;
&lt;/form&gt;
</code></pre>

<p>I am getting formname,checkboxid,textid in alerts inside the javascript function... But
the problem is with the line 
<code>for (var i=0; i &lt; document.formId.checkboxId.length; i++)</code></p>

<p>Webdeveloper toolbar shows this error</p>

<p><code>document.formId is undefined</code></p>
