Post-thumbnails are rotated when uploaded via iPhone

I’m uploading a photo via the function below. All of the full size images show up correctly however, if I upload a photo in portrait, the post-thumbnails are rotated 90degrees. Am I doing something wrong or is this a bug? It seems as if the exif data is not read when creating thumbnails.

function add_food_photo( $formData = false, $product_id = false, $field = false ) {

	if ($product_id && $_FILES[$field]['size'] > 0) {

		require_once(ABSPATH . 'wp-admin/includes/file.php');

		// Get the type of the uploaded file. This is returned as "type/extension"
		$check_file_type = wp_check_filetype(basename($_FILES[$field]['name']));
        $uploaded_file_type = $check_file_type['type'];

		// Set an array containing a list of acceptable formats
        $allowed_file_types = array('image/jpg','image/jpeg','image/gif','image/png');

		// If the uploaded file is the right format
        if(in_array($uploaded_file_type, $allowed_file_types)) {

		$upload_dir = wp_upload_dir();

		$file_upload_data = wp_handle_upload($_FILES[$field], array('test_form' => FALSE) );

		if ( $file_upload_data ) {

			// delete all attachements

			//$attached_image = get_children( "post_parent=".$product_id."&post_type=attachment&post_mime_type=image&numberposts=1" );
				$attached_image = get_children( "post_parent=".$product_id."&post_type=attachment&post_mime_type=image&numberposts=1" );
				if ($attached_image) {
					foreach ($attached_image as $attachment_id => $attachment) {
					wp_delete_attachment($attachment_id, true);
				}
			}

	//		print_r ($file_upload_data); exit;

			$image_url = $file_upload_data['file'];

			$image_data = file_get_contents($image_url);

			$filename = basename($image_url);
			if(wp_mkdir_p($upload_dir['path']))
			    $file = $upload_dir['path'] . '/' . $filename;
			else
			    $file = $upload_dir['basedir'] . '/' . $filename;
			file_put_contents($file, $image_data);

			$wp_filetype = wp_check_filetype($filename, null );
			$attachment = array(
			    'post_mime_type' => $wp_filetype['type'],
			    'post_title' => sanitize_file_name($filename),
			    'post_content' => '',
			    'post_status' => 'inherit'
			);
			$attach_id = wp_insert_attachment( $attachment, $file, $product_id );
			require_once(ABSPATH . 'wp-admin/includes/image.php');
			$attach_data = wp_generate_attachment_metadata( $attach_id, $file );
			wp_update_attachment_metadata( $attach_id, $attach_data );

			set_post_thumbnail($product_id, $attach_id);

			// Set the feedback flag to false, since the upload was successful
            $upload_feedback = false;

		} else { // Didn't get a upload directory
				// wp_handle_upload returned some kind of error.
				$upload_feedback = 'There was an erorr uploading your image';
		}
	  } else { // Wrong file type uploaded
             $upload_feedback = 'Please upload only image files (jpg, gif or png).';
	  }
	} else { // No file submitted
		$upload_feedback = false;
	}
 return  $upload_feedback;
}