What is wrong with this code? (Drupal)

What is wrong with this code? (Drupal)

I use this code in my subtheme page--front.tpl file, but I can not see any
message on my front page like my code bellow.
<?php
$flag = drupal_is_front_page();
if ($flag) {
drupal_set_message("Welcome to front page of this site.");
}
else
{
drupal_set_message("Now you are in page other than front page.");
}
?>