What Does Error, Unexpected end of file mean?

Question

Here is the code:

<?php

session_start();

$redCo = $_SESSION['tagRedFamily'];
$blueCo = $_SESSION['tagBlueFamily'];
$greenCo = $_SESSION['tagGreenFamily'];

if ($redCo == true) {

    echo "0";

if ($blueCo == true) {

    echo "1";

if ($greenCo == true) {

    echo "2";

}

?>

And it gives me the following error:

Parse error: syntax error, unexpected end of file in /Applications/XAMPP/xamppfiles/htdocs/Experiments/Tags/tagWorker.php on line 26

Does anyone know why?