If you want to change the .php file extensions to say .foo then you could try the following in an htaccess file to get the .foo files to evaluate as .php files:
Code:
<Files *.foo>
ForceType application/x-httpd-php
</Files>
Of course you'd need to check the code too for any use of .php in paths and links and change those to .foo also.
If you want to change the search.php filename to search with no extension then you could instead try the following to get search to evaluate as the search.php file:
Code:
<Files search>
ForceType application/x-httpd-php
AcceptPathInfo On
</Files>
Where SEARCH_PAGE is set to search in the PhpDig config file.