The version number is part of the name of the installation package (e.g., php-4.4.0.tar.gz is the distribution for PHP v4.4.0) . You can also enter "php -v" at the command line.
Another possibility is that you haven't properly configured your server to pass requests for PHP pages on to PHP for processing. a page that reads
<?php
phpinfo();
?>
that isn't processed by PHP would just get sent to the browser as
<?php
phpinfo();
?>
And that would be the "HTML" that the browser receives and tries to render. And since <?php> isn't a valid HTML tag, it won't be rendered and all you'd see is