Redirect my first page "index.php" to another page

[darsanha]

I want to redirect my page "index.php" which is the first page (automatic) site to a page that is called "exposition.php."
I can not do it ...
I tried to put PHP code in my page "template.php"

Code:

<? php
header ('Location: http://www.lematgalerie.com/exposition.php');
?>

But when I type the URL of the site I have a 404

Is this a good method or should I add some code in the file. Htacces?

thank you