Why do I need the isset() function in php?

Question

I am trying to understand the difference between this:

if (isset($_POST[\'Submit\'])) { 
  //do something
}

and

if ($_POST[         


        

Answer 1

In your 2nd example, PHP will issue a notice (on E_NOTICE or stricter) if that key is not set for $_POST.

Also see this question on Stack Overflow.