Using .htaccess to make all .html pages to run as .php files?

Create a .htaccess file at the root of your website and add this line:

[Apache2 @ Ubuntu/Debian: use this directive]

AddType application/x-httpd-php .html .htm

Or, from comment below:

AddType application/x-httpd-php5 .html .htm

If your are running PHP as CGI (probably not the case), you should write instead:

AddHandler application/x-httpd-php .html .htm 

In My Godaddy Server the following code worked

Options +ExecCGIAddType application/x-httpd-php .php .htmlAddHandler x-httpd-php5 .php .html

You may also use the H or T flag of mod_rewrite to force all .html files to be parsed by php handler :

using H (Handler) flag:

 RewriteEngine onRewriteRule \.(html|htm)$ - [H=application/x-httpd-php5]

using T (Type) flag :

 RewriteEngine onRewriteRule \.(html|htm)$ - [T=application/x-httpd-php5]

Or you can add more extensions to the rule pattern seprated by a pipe | that you want to be parsed by php handler

ex :

RewriteRule \.(html|htm|txt|foo)$ - [T=application/x-httpd-php5]

the example above will change the mime type of files that end with .html , .htm , .txt , .foo to php.

Note : on some servers you will have to change php5 to php to get this example to work in handler string:

Change it

[T=application/x-httpd-php5]

to

[T=application/x-httpd-php]