Drupal - Check if the page is the front page in a template

You should not declare a function in a Drupal template. Instead, you should just refer to that function:

<?php
if (drupal_is_front_page()) {
    ?><h1>Test</h1><?php
}
?>

drupal_is_front_page() returns boolean value.

<?php if(drupal_is_front_page()): ?>
<h1>TEST</h1>
<?php endif; ?>