how make varaible ( $message ) contain multi odds

i have many value in form php
i want send email and auto replay email via ( mail function )
problem is i want send many odds
i mean the form sent email by content by different possibilities
– send link program 1 only
– send link program 2 only
– send link program 3 only
– send link program 1-2 only
– send link program 1 – 3 only
– send link program 2 -3 only
– send link program 1-2-3

this code php

HTML:

<?php

$first_name = $_POST[‘first_name_1′];

 $last_name =…

how make varaible ( $message ) contain multi odds

See original post by lost23