When to use index.php instead of index.html
You will
have to choose the PHP extension (.php) when you want
php code to be executed in the file. PHP code is code
between the opening <?php
or <? and the closing ?> tags.
When NO PHP code should be executed you can
use the .html extension.
Usually
when using the .php extension you are telling the web
server, that it should use a php interpreter to
process the file before it will be delivered to the browser. The php interpreter will then replace all content between the
<?php and ?> by the
output of the PHP code. Just as if you wrote it manually. The processed file
will then be delivered to the browser.
However,
using the .php extension to tell the web server to
process php code is configurable. If you want you can
use other file extensions too.
There is
another thing that should be pointed out. When you only type the url path (without a filename) like :
http://www.myserver.com/
There is
an order of extensions (filenames) which the webserver (apache) searches for an
index document. For example an apache config may
contain a section like:
<IfModule mod_dir.c>
DirectoryIndex index.html index.cgi
index.pl index.php index.xhtml
index.htm
</IfModule>
The above
means that the index document is searched in the order above, and it if you
place an index.html and a index.php in the same
folder - and having the configuration above - always the index.html would be
delivered by the server.