im new here. and i new to php. now i want to make a selectable seat where when user click it will change color and update the value "status" to the database. but now i got this error
Uncaught TypeError: Cannot read property 'src' of null
here is my code
<script language="javascript">
function changeImage(pos) {
var pos = <?php echo(json_encode($data[pos])); ?>;
if (document.getElementById(pos).src == "$base/images/kuning.png")
{
document.getElementById(pos).src = "$base/images/hijau.png";
alert("ok1");
}
else if (document.getElementById(pos).src == "$base/images/hijau.png")
{
document.getElementById(pos).src = "$base/images/merah.png";
alert("ok2");
}
else if (document.getElementById(pos).src == "$base/images/merah.png")
{
document.getElementById(pos).src = "$base/images/kuning.png";
alert("ok3");
}
}
</script>
<?php
$q = "SELECT * FROM schedule WHERE inv_id=1";
$sql = mysql_query($q);
echo "<table>";
while($data=mysql_fetch_array($sql))
{
if($data["status"]=="done")
{
$image = "<a href='#'><img src='$base/images/hijau.png' id='$data[pos]' border='0' width='33' height='26' alt='$data[pos]' onclick='changeImage($data[pos])'/></a>";
}
elseif($data["status"]=="onschedule")
{
$image = "<a href='#'><img src='$base/images/kuning.png' id='$data[pos]' border='0' width='33' height='26' alt='$data[pos]' onclick='changeImage()'/></a>";
}
elseif($data["status"]=="late")
{
$image = "<a href='#'><img src='$base/images/merah.png' id='$data[pos]' border='0' width='33' height='26' alt='$data[pos]' onclick='changeImage()'/></a>";
}
echo "<td><center>$image</br>$data[date]</center></td>";
}
echo "</table>";
?>