File upload problem

I'm trying to upload a file using a form the upload code I'm using is //====================================================== <?php // settings $base_img_dir = "http://localhost/app_images/"; include("db.php"); // generate unique id for use in filename $uniq =uniqid(""); $filename = $base_img_dir.$uniq; move_uploaded_file($HTTP_POST_FILES["file"]["tmp_name"], $filename); ?> //====================================================== this code generated the following erro //====================================================== Warning: move_uploaded_file(http://localhost/app_images/4139de74488ad): failed to open stream: HTTP wrapper does not support writeable connections. in C:\Program Files\Apache Group\Apache2\htdocs\upload.php on line 25 Warning: move_uploaded_file(): Unable to move 'C:\WINDOWS\php11.tmp' to 'http://localhost/app_images/4139de74488ad' in C:\Program Files\Apache Group\Apache2\htdocs\upload.php on line 25 //====================================================== thanks in advance