RE: [PHP] Understanding session variables with input field and register_global

[snip]
I've an input field in a form

<input name="username" type="text" ...

and with register_global I can use this field in PHP as variable
$username. Yet if I use a session variable

$_SESSION['username'] = 'value'

the variable $username gets the same value. On the other side when I
enter a value in the input field, the session variable isn't changed. So

how can I set the session variable from the input field after it has
changed?
[/snip]

$_SESSION['username'] = $username;

But really, you should turn off register_globals (holy war will not
ensue at this point, everyone knows the value).