Error while renaming and uploading file using PHP - Undefined index

Question

Below is the given code. I want to renamen the file before uploading. On submitting it is showing error: Undefined index.

        if($_FILES['FPScreenShot']['name']==true)
        {
            $SPPic = ($_FILES['FPScreenShot']['name']);
            $curTime = time();
            $NewPriorPic = "prior";
            $NewPriorPic = $NewPriorPic.$SGeiNo;
            $NewPriorPic = $NewPriorPic.$SSurgDt;
            $NewPriorPic = $NewPriorPic.$curTime;

            move_uploaded_file($_FILES['FPScreenShot']['tmp_name'] , "upload_pictures/".$_FILES['$NewPriorPic']['name']);
        }
    else
        {
            $SPPic = "NIL";
        }

Answer 1

Solved. For future reference, if anyone needed.

    if($_FILES['FPScreenShot']['name']==true)
        {
            $SPPic = ($_FILES['FPScreenShot']['name']);
            $ext = pathinfo($SPPic, PATHINFO_EXTENSION);
            $curTime = time();
            $NewPriorPic = "prior";
            $NewPriorPic = $NewPriorPic.$SGeiNo;
            $NewPriorPic = $NewPriorPic.$SSurgDt;
            $NewPriorPic = $NewPriorPic.$curTime;
            $NewPriorPic = $NewPriorPic.".".$ext;
            $location = "upload_pictures/";

            move_uploaded_file($_FILES['FPScreenShot']['tmp_name'], $location.$NewPriorPic);
        }