tags of a similar ilk

For custom modules and well-defined roles, we sometimes want to check to see if a user is in the a particular role.

The easiest way to do so is to check the user's roles array:

global $user;

if (!empty($user->uid)) {
  if (in_array('desiredRole', $user->roles)) {
    // user is in role, perform desired actions here 
  }
}

The $user object is in the global name space, so using the global declaration in a function is necessary.

If the user isn't logged in, the $user->uid value will be 0. empty returns true for 0/null/empty values, as explained on php.net. in_array checks the desiredRole is in the user's roles.