NamePros.Com - [PHP] image uploading

I currently have this which works pretty dam well.
Although i want to allow more than just jpg files to be uploaded, i also want the names to be proper randomized as right now it keeps the same name so there could be many conflicts :(

PHP Code:

    $imagename = $_FILES['new_image']['name'];

 
        $source = $_FILES['new_image']['tmp_name'];

 
        $target = "images/uploads/".$imagename;

 
        move_uploaded_file($source, $target);

 
              

 
        $imagepath = $imagename;

 
        $save = "images/uploads/" . $imagepath; //This is the new file you saving

 
        $file = "images/uploads/" . $imagepath; //This is the original file

 
 
 
        list($width, $height) = getimagesize($file) ; 

 
                                                         

 
        $diff = $width;

 
 
 
        $save = "images/uploads/thumb_" . $imagepath; //This is the new file you saving

 
        $file = "images/uploads/" . $imagepath; //This is the original file

 
 
 
        list($width, $height) = getimagesize($file) ; 

 
                                                         

 
        $tn = imagecreatetruecolor(150, 150) ; 

 
        $image = imagecreatefromjpeg($file) ; 

 
        imagecopyresampled($tn, $image, 0, 0, 0, 0, 150, 150, $width, $height) ; 

 
                                                        

 
        imagejpeg($tn, $save, 100) ; 

 
        

 
        $sql = "UPDATE `listings` SET `screenshot` = '{$imagepath}', `thumbnail_screenshot` = 'thumb_{$imagepath}' WHERE `scriptid` = '{$_GET['lid']}'";

 
        

 
        mysql_query($sql);