PHP FILTER VALIDATE EMAIL does not work correctly

Question

I employ PHP 5.3.10. Here is the code:

<?php
$email = "test@example.c";
if (filter_var($email, FILTER_VALIDATE_EMAIL))
        echo "Email: ".$email." correct";
else
        echo "email not correct";
?>

"Email: test@example.c correct," it responds.

According to this list: https://data.iana.org/TLD/tlds-alpha-by-domain.txt , I'm not aware of any top level domains (TLDs) that are only one character in length.

Therefore, is the FILTER VALIDATE EMAIL filter functioning properly or not?