variable won't display contents

[jarow]

$user = $_POST['username']

I have created a login redirect variable (within a php statement) which works if written this way:

$redirect = "admin_$user.php"

but does NOT work if I write it this way

$redirect = "$user_admin.php"

Why does username appear correctly in the first example but not in the second?

Many thanks

Jarow

[laserlight]

because
"$user_admin.php"
is equivalent to

$user_admin . '.php'

so why not use:

$redirect = $user . '_admin.php';
?
or even

$redirect = $POST['username'] . 'admin.php';
?

[jarow]

Thanks laserlight....works well now