Darren Chow

MB Creation

If you want to promote your brand new newsletter functionnality, display advertising on your homepage or get more Facebook fans you can use Simple Popup Manager to “popup” a message all over your content in a lovely “lightbox effect”. You can customize your message using a WP editor and of course specify the width and the height of the message box. You can limit the display off the message on either session or days basis.
For more information, please visit <a href="http://www.darrenchow.com/plugins/ez-popup-manager" title="EZ Popup Manager" rel="nofollow ugc">EZ Popup Manager Plugin Site</a>

EZ Popup Manager

EZ Popup Manager allows you to easily display a simple message box on your WordPress front page.

Dreb Bitanghol

This field will provide you more options and flexibility on how you would like to present an instruction or message to your client’s (or site in general) admin interface.
Features:
<ul>
<li>Support PHP.</li>
<li>Option to hide label when field is displayed.</li>
</ul>
Compatible with Advanced Custom Fields:
<ul>
<li>4 (tested up to 4.4.6)</li>
<li>5 (PRO, tested up to 5.3.7)</li>
</ul>
PS: You need <a href="https://wordpress.org/plugins/advanced-custom-fields/" rel="ugc">Advanced Custom Fields</a> installed to use this.
PPS: Even more awesome if you have <a href="http://www.advancedcustomfields.com/pro/" rel="nofollow ugc">Advanced Custom Fields PRO</a> installed.
Important note: Use this with utmost care.

ACF Enhanced Message Field

Exactly what I needed

Exactly what I needed. You could improve the plugin by making the textarea field look more like an IDE, with system fonts, syntax highlights and so on.

Perfect

Awesome!!

Adds an enhanced version of the default Message field to accept PHP and certainly no wpauto().

EZ Popup Manager vs ACF Enhanced Message Field