Ever wanted to add Php to your pages and post. For those that like to keep control of their own mail list this is very important to do but wordpress does not allow it for security reasons. If you want to add Php you would have to use external files and then use shortcode (as explained by Wordpress API) in order to add Php. This is a very painful and useless process though because it uses more processes and more pages to pull the information, thus making your site slower.
A very good and secured plugin to use to add Php directly to your pages and post does exist though. I have tested it and it works perfect with no shortcode needed or external pages. So for someone that wants to have a mail list, confirm page, and thank you page without using external files this is a great plugin.
The PHP Execution Plugin is a WordPress plugin which allows users to write php code inside of their posts and pages. Embedded php code will be executed when the post is shown. In doing so, the plugin offers the possibility to utilize dynamic content inside of posts.
In contrast to other plugins with the same aim, this one integrates well with WordPress' visual editor. So there is no need to turn off the visual editor in order to edit your php code. Additionally it provides an admin section which lets administrators edit the blog users' php execution rights easily. The plugin also automatically prevents users with no php execution rights from editing posts or pages of users with these rights. It thus fixes a possible security leak where people without php execution rights can still execute code with editing other users' posts.
Download the plugin here - Php Execute Plugin For Wordpress
Edited 10-16-2014: The above links to a plugin that has not been updated. You may find more updated plugins for wordpress here: https://wordpress.org/plugins/search...embed+php+code