The php syntax starts with
<?php
and it may or may not end with
?>
Php files can include only php code, only html code or mix both.
When there is only php code in the file the closing tag "?>" is not required.
The php interpreter starts processing the file when it sees the opening tag and will go to the end of file or until it hits the closing tag.
So if the file only has php code in it it is acceptable not to use the php closing tag.
https://secure.php.net/basic-syntax.phptags