When accessing a PHP web page on Apache 2 the source is returned as a text file with the MIME type of application/x-trash.

Apache 2 is using MultiViews to negotiate an unexpected extension for the requested web page using /etc/mime.types e.g.

In /etc/mime.types:

application/x-trash    ~ % bak old sik

In the httpd.conf/apache2.conf:

<Directory /var/www/public_html>
   Options +MultiViews
</Directory>

Will return index.php.old as application/x-trash when /index.php or /index is requested.

Content Negotiation
http://httpd.apache.org/docs/2.0/content-negotiation.html