php vars declared on header only work on header not on footer and content

Hellow, my problem comes because i´m developing a multi language site, so i use php includes for change titles and texts of static contents. I created a folder lang with es.php, en.php and de.php and load one of this depends the language by url segment. The problem is the php vars only works on header and doesn´t work in the rest of page.

Example:

header:

<?php $info=”{last_segment}”; switch ($info) { case “en”: $lang=”_en”; include(“lang/en.php”); break;

case “de”: $lang=”_de”; include(“lang/de.php”); break;

default : $lang=”“; include(“lang/es.php”); } ?>

and for example en.php contains $about=’We are a company…..’; if i put <?=$about;?> on header works correctly but if i put on any template or on a footer page doesn´t work and show me a php error:

“A PHP Error was encountered

Severity: Notice

Message: Undefined variable: about”

Who can i solve this???????

Thanks