如何修复未定义的索引

Question

   //here are some of my declarations
        $sex   = @$_POST["sex"];
            $bdate = @$_POST["bdate"];
            $firstname = @$_POST["firstname"];
            $lastname  = @$_POST["lastname"];
            $profPic   = @$_FILES["prof-pic"];

        <div class="form-group">
                <label class="control-label col-sm-2" for="name">Profile Picture</label>
            <div class="col-sm-5"> 

注意：未定义的索引： C：\ xampp \ htdocs \ slamB \ profile.php 中的profPic 152
/＆gt;

              <input type="text" class="form-control" name="lastname" value="<?=$user['profPic']?>"  disabled>

            </div>
            </div>