File upload with validation issue

[monki_SF]

Im using the following to upload a single image file. The form works to limit the size of the file (If the file is over 500k it won't be uploaded). However - my error handling doesn't seem to be working correctly. I've left out the code thats not associated with the image upload below for the most part.

Anyone have any ideas?

<script language=javascript>
extArray = new Array(".jpg", ".jpeg",".gif");  //".png", , ".gif"
function callSave()
{
    if(!isCurrency(document.frmlisting.txtlistingprice.value)){
        alert("Price: Incorrect data");
        document.frmlisting.txtlistingprice.select();
		return;
    }
	if(isBlank(document.frmlisting.txtlistingtitle.value)){
    	alert("Title is Required");
        document.frmlisting.txtlistingtitle.focus();
    	return;
    }
	if(!isBlank(document.frmlisting.txtlistingimage.value)){
	    if(!isValidFile(document.frmlisting.txtlistingimage.value)){
	        alert("Selected file is not a vaild image type. \nPlease select "+ (extArray.join("  ").toUpperCase())+ " files. ");
	        document.frmlisting.txtlistingimage.select();
	        return;
	    }
    }
	if(isBlank(document.frmlisting.txtlistingemail.value)){
        alert("Email is Required");
        document.frmlisting.txtlistingemail.select();
		return;

}
if(!isEmail(document.frmlisting.txtlistingemail.value)){
    alert("Email: Incorrect data");
    document.frmlisting.txtlistingemail.select();
    return;
}

document.frmlisting.action="listingsubmit.php";
document.frmlisting.submit();
}
</script>
<FORM name="frmlisting" method="post" enctype="multipart/form-data">
<input type="hidden" name="MAX_FILE_SIZE" value="500000">
<Input type="file" name="txtlistingimage" style="WIDTH: 275px; HEIGHT: 20px" size="39" maxlength="100">
	             <Input type=hidden name="mode" value="<?=$mode?>">
	             <input type=hidden name="l_id" value="<?=$l_id?>">
	             <input type=hidden name="c_id" value="<?=$c_id?>">
                    <input type=hidden name="cboCity" value="<?=$intcityid?>">
                    <input type=hidden name="txtpreviousimage" value="<?=$listingimage?>">
                    <input type=hidden name="txtfrmpg" value='<?=$frmpg?>'>
<input type="button" class="btn_text" value="Preview" onclick="javascript:callSave();" style="border:solid-1px; color: #333333 ">

The processor "listingsubmit.php"

<?
$frmpg = $HTTP_POST_VARS['txtfrmpg'];
$dirupload = "images/listing/";

switch ($mode){
case "Add":
//-- GET SIZE OF UPLOAD IMAGE

/*== only allow images smaller than 600 x 600 ==*/
$imgsize = GetImageSize('txtlistingimage');

/*== check size  0=width, 1=height ==*/
if (($imgsize[0] > 600) || ($imgsize[1] > 600))
{
      /*== if an error occurs the file could not
           be written, read or possibly does not exist ==*/
      print "Your File is to large. Maximum file dimensions are 600px x 600px.";
      exit();
   }

$max_filesize_k = ($max_filesize / 500);

if($_FILES['txtlistingimage']['size'] > $max_filesize)
{
   echo "Your file is too large.  Files may be up to ".$max_filesize_k."K\n";
   include("listingentry.php");
   exit;
}
//-- END GET SIZE OF UPLOAD IMAGE

    if($HTTP_POST_FILES['txtlistingimage']['name'] == ""){
        $listing_image = "";
    }else{
        $listing_image = getfilename($HTTP_POST_FILES['txtlistingimage']['name'],1);
        copy ( $HTTP_POST_FILES['txtlistingimage']['tmp_name'],$dirupload.$listing_image)
        or $msgid=2;
    }