How to send e-mail messages using PHP?

<?php
    mail("recipient@example.com",
        "This is the message subject",
        "This is the message body",
        "From: sender@example.com" . "\r\n" . "Content-Type: text/plain; charset=utf-8",
        "-fsender@example.com");
?>

How to change the default directory index page using an .htaccess file?

You can use the DirectoryIndex directive in an .htaccess file 
to specify a custom file or files that the web server looks for 
when a visitor requests a directory. To enable the DirectoryIndex 
directive, use a text editor to modify the .htaccess file as 
follows. Replace filename with the file that you want to 
display whenever a user requests the directory:

DirectoryIndex filename

You can also specify multiple filenames, and the web server
 will search for each file until it finds a match. Consider 
this example directive:

DirectoryIndex index.php index.html index.htm

How to enable and disable directory index listings using an .htaccess file?

Enable directory index listings
In some cases, however, you may want to enable index listings for a directory. 
To do this, use a text editor to add the following line to the .htaccess file:

Options +Indexes

This directive enables standard indexing, where the index listing shows 
only the filenames. You can also enable “fancy” indexing, where the 
index listing shows filenames, their filesizes, and when they were 
last modified. To do this, add the following line to the .htaccess file:

IndexOptions +FancyIndexing