php file upload not working right

I have been assigned the task of fixing an older php site since it has been moved to a newer server. The server it is on now doesn't allow globalized variables and that's pretty much all this site was running off of. When trying to upload an image, my sql statement is showing everything but the id for the listing I am adding the image to. I was hoping someone could help me figure this out.

This is my upload function:

function upload(){
global $imagefolder, $id;
global $tbl_units;

include "globalizePOSTGET.php";

// $uid = uuid();
$minsize = 5000;            // 5kb
$maxsize = 3000000;     // 3mb
$ext = explode('.',basename($_FILES['userfile']['name']));
$ext = $ext[count($ext)-1];
$ext = strtolower($ext);

if ($ext != "jpg" && $ext != "jpeg" && $ext != "png") {
    echo "<script> alert('Image is not a png or jpeg format'); </script>";
    return false;
}

$imagename = $_POST['id']."_img".$_FILES['img'].".$ext";
$imagename2 = "X_".$imagename;
$uploadfile = $imagefolder . $imagename;
$uploadfile2 = $imagefolder . $imagename2;
$uploadthumb = $imagefolder . "tn_" . $imagename;

if (file_exists($uploadfile)) unlink($uploadfile);
if (file_exists($uploadthumb)) unlink($uploadthumb);

if (file_exists($uploadfile)) { 
    echo "<script> alert('Image already exists!'); </script>";
}
else
{
    if(is_uploaded_file($_FILES['userfile']['tmp_name'])) {
        // check the file is less than the maximum file size
        if($_FILES['userfile']['size'] < $maxsize) {
            $imgData = addslashes(file_get_contents($_FILES['userfile']['tmp_name']));      // prepare the image for insertion
            $size = getimagesize($_FILES['userfile']['tmp_name']);          // get the image info..
            if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile2)) {
                $Image = @imagecreatefromjpeg($uploadfile2);
                if ($Image) {
                 $img_height = imagesy($Image);
                 $img_width = imagesx($Image);
                 imagedestroy($Image);
                }

                if ($img_height > $img_width) {         // portrait  
                    $tempMultiplier = 150 / $img_height;
                    $tempMultiplierFull = 600 / $img_height;
                } else {
                    $tempMultiplier = 150 / $img_width;
                    $tempMultiplierFull = 600 / $img_width;
                }

                $imageHeight = $img_height * $tempMultiplier;
                $imageWidth = $img_width * $tempMultiplier;
                $fullimageHeight = $img_height * $tempMultiplierFull;
                $fullimageWidth = $img_width * $tempMultiplierFull;
                createthumb($imagename2,"tn_".$imagename,$imageWidth,$imageHeight);

                if($_FILES['userfile']['size'] > $minsize) {
                    createthumb($imagename2,$imagename,$fullimageWidth,$fullimageHeight);
                    if (file_exists($uploadfile2)) unlink($uploadfile2);
                } else {
                    rename($uploadfile2, $uploadfile);
                }

                $sql = "UPDATE $tbl_units SET photo".$_FILES['img']." = \"" . $imagename . "\" WHERE id = " . $_POST['id'];
                echo $sql;
                if(!mysql_query($sql)) {
                    echo "<script> alert('Unable to upload file'); </script>";
                } else {
                    ?> <script>location.replace('memonly.php?action=edit_record&id=<?php echo $id; ?>');</script> <?php
                }
            }
        }   else {
            // if the file is not less than the maximum allowed, print an error
            $file_n = basename($_FILES['userfile']['name']);
            $file_s = $_FILES['userfile']['size'];
            ?>
            <script> alert("File exceeds the maximum limit of <?php echo $maxsize; ?>\nFile <?php echo $file_n; ?> is <?php echo $file_s; ?>");</script>
            <?php
        }
    }
}
}

I am echoing the sql statement on the line that is giving me the error, I think. After clicking on submit, the page tells me Unable to upload file'. Which is why I echoed the sql there. I end up with a sql statement looking like this:UPDATE member_units SET photo = "_img.jpg" WHERE id = `

Someone please help me! I am very inexperienced in PHP and I have no idea what to do here.

Here is the form that is doing the uploading:

<form enctype="multipart/form-data" action="<?php echo $_SERVER['PHP_SELF']?>" method="post">
<input type="hidden" name="_submit_check" value="1" /> 
<input type="hidden" name="id" value="<?php echo $id; ?>" />
<input type="hidden" name="img" value="<?php echo $img; ?>" />
Image URL: <input type="file" name="userfile" value=""  style="font-size: 10px; width: 100%;">
<input type="submit" value="Submit" onClick="return validate();">&nbsp;
<input type="button" value="Cancel" onClick="location.href='/memonly.php?action=edit_record<?php echo "&id=$id&memberid=$memberid"; ?>';">
</form>