I want to implement following logic - if there is an array, lets say "portfolioHistoryResults" in session, then loop it and display else do nothing.

This is not at all a big deal, but I am new to PHP and looks like PHP doesn't work the way other scripting languages worok becayse when I use following code 

```
if ($_SESSION["portfolioHistoryResults"] != null
    && $_SESSION["portfolioHistoryResults"] != undefined)
{

```

Then I end up with `Notice: Undefined index: portfolioHistoryResults in /home/abc/vhosts/localhost/views/common/portfolio.php on line 14`.

At the time of executing that line I have my session object created but in certain cases it will not have have "portfolioHistoryResults" variable inside it. Looks like PHP is expecting to be always present or defined.

Can anybody throw light on how this works in PHP.