退出时导致“ 500-内部服务器错误”的php语句

Question

I have this function in index.php...

function getCurrentUserID(){
  var currentUserID;
  if (confirmLogin()){
    currentUserID = "<?php echo htmlentities($_SESSION['user_id']); ?>";
  } else {
    currentUserID=-1;
  }
  return currentUserID;
}

When I'm logged in it works nicely and returns the user_id. The second I log out (which refreshes index.php) I hit a "500 - Internal server error" that I can only resolve by DELETING the php line from the function (if I even comment out using javascripts // notation I still see the 500 error). Once I've deleted the line I can then refresh the page, log back in, and if I want add php reference to the function again!

Does anyone have any idea how to resolve this problem permanently though? I don't know why the php script is problematic since it's inside a "confirmLogin()" check (not to the mention the fact it's sometimes commented out altogether!) Feels like I might have put this in the wrong place but I really don't know what the right place is! Thanks for any thoughts.

Answer 1

The PHP code is being parsed server-side, so way before any JS comes to life - that's why it doesn't matter if your line is inside the JS function.

What causes your problem is fact you're trying to access an array element under the non-existing key. In PHP it is illegal. The quickest fix is to check, if the value is set before echoing it: <?php isset($_SESSION['user_id']) ? echo $_SESSION['user_id' : echo '-1'; ?> <?php isset($_SESSION['user_id']) ? echo $_SESSION['user_id' : echo '-1'; ?>

This will resolve your issue but, in general, I would try to avoid mixing programming languages like that.