Checking for unique values in $_POST?

[duckduckgoose]

I have a form with text fields that people fill in. How can I ensure that the value in each field is unique?

For example, if the user enters:

Email1 = [e-mail]
Email2 = [e-mail]
Email3 = [e-mail]
Email4 = [e-mail]
Email5 = [e-mail]

How can I filter it out so that it shows only:

Email1 = [e-mail]
Email2 = [e-mail]
Email3 = [e-mail]
Email5 = [e-mail]

[NogDog]

One possibility:

$emails = array_unique(
  array(
    $_POST['email1'],
    $_POST['email2'],
    $_POST['email3'],
    $_POST['email4'],
    $_POST['email5']
  )
);