mayel2b

Helps you more effectively edit your themes or plugins when you only have access to a browser, by enabling syntax highlighting in WordPress’ integrated source code editors. Supports PHP, HTML, CSS and JavaScript.
Please provide any feedback at http://anetech.eu/power-code-editor/
Everything is done in JavaScript on the client side.
At this time, the following browsers are supported: 
* Firefox 1.5 or higher 
* Internet Explorer 6 or higher 
* Safari 3 or higher 
* Opera 9.52 or higher 
* Chrome
Licensed under the GNU GPL v2.
Uses the excellent CodeMirror JS library : 
http://marijn.haverbeke.nl/codemirror/

Power Code Editor

Enables syntax highlighting in the integrated source code editors. Supports PHP, HTML, CSS and JS.

rewish

This plugin will not be update anymore.
Install the <a href="https://wordpress.org/plugins/wp-emmet/" rel="ugc">WP Emmet</a> instead and use the Emmet (previously known as Zen Coding).

WP Zen-Coding

WP Zen-Coding is a awesome Zen-Coding plugin for WP admin page.

Power Code Editor vs WP Zen-Coding