javascript onchange in php while loop - php

Question

I have a form where radio types are generated inside a PHP while loop. Depending on which radio is selected, java script queries MySQL to get the correct value and return it to a text box. It works except for onload. OnLoad returns the incorrect value, whatever was first in the while loop iteration. Onchange will return the right value.
How can I get onload to return the right value? I am using "checked" in my radio throughout the while iteration so that one circle is always checked. It doesn't matter to me which radio is checked by default. Using checked in the while iteration always makes the last iteration checked which is OK, but it is displaying the value for the first.
here is my code.
<script type="text/javascript">
function getNextcheck(str)
{
if (str=="")
{
document.getElementById("nextcheck").innerHTML="";
return;
}
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("nextcheck").innerHTML=xmlhttp.responseText;
}
}
xmlhttp.open("GET","getnextcheck.php?id="+str,true);
xmlhttp.send();
}
window.onload = function() {
document.getElementsByName('ID')[0].onchange();
}
</script>
And the file getnextcheck.php it pulls
<?php
include $_SERVER['DOCUMENT_ROOT']."/connect.php";
$result = mysql_query("SELECT * FROM bankaccount WHERE ID = '$_GET[id]'");
$row = mysql_fetch_array($result);
$nextcheck = $row['next_check'];
if (empty($nextcheck)) { $nextcheck = 0; }
echo "<tr><td>Check Number <input type=\"text\" name=\"checkno\" value=\"".$nextcheck."\" /></td></tr>";
And the radio inside the form.
while($row2 = mysql_fetch_array($result2)) {
$id = $row2['ID'];
echo "<tr><td><input type=\"radio\" name=\"ID\" value=\"".$row2['ID']."\" onchange=\"getNextcheck(this.value)\" checked></td><td>".$row2['name']."</td><td>".$row2['acctnum']."</td>";
}
Thank you for your help.

Answer 1

make only first radio check
<?
$i=0;
while($row2 = mysql_fetch_array($result2)) {
$id = $row2['ID'];
$checked = $i?'':'checked';
echo "<tr><td><input type=\"radio\" name=\"ID\" value=\"".$row2['ID']."\" onchange=\"getNextcheck(this.value)\" {$checked}></td><td>".$row2['name']."</td><td>".$row2['acctnum']."</td>";
$i=1;
}
?>