The Advanced WordPress Theme Editor plugin will allow you to edit your theme directly in your blog admin section but with a better experience since it will format and highlight your source code with nice colours.
The plugin is compatible with WP 2.8 and less and is based on the Edit Area script that supports at least PHP, CSS, JS and many more file types.

Advanced WordPress Theme Editor

This plugin will improve your experience when editing yout wp themes since it will format and highlight your source code with nice colours.

Thomas Lloancy

Simple Editor Control silently records every file change made through the WordPress built-in plugin editor and theme editor. For each save it stores the diff, the editor who made it, and the timestamp — giving you a full, browsable history.
Features
<ul>
<li>Automatic tracking — no setup required. Every save through the WP file editor is captured.</li>
<li>Git-style diff viewer with side-by-side and line-by-line modes.</li>
<li>Adjustable context lines (0, 3, 5, 10, 20).</li>
<li>Point-in-time file recovery — download any file as it existed at any past revision.</li>
<li>Works with all plugins and all active themes.</li>
<li>Accurate LCS-based diff engine (same algorithm as GNU diff / git) — handles insertions, deletions and replacements correctly.</li>
<li>Fully translatable.</li>
</ul>
Use cases
<ul>
<li>See exactly what changed when something broke.</li>
<li>Verify that no unauthorised changes were made to your plugin or theme files.</li>
<li>Recover a previous version of a file without restoring a full backup.</li>
</ul>

Simple Editor Control


Wordpress editor is very handy, and you can see the difference made when a plugin or theme was edited using that tool. It's my plugin and i like it


Go and download it

Audit trail and git-style diff viewer for every file change made through the WordPress plugin and theme file editor.

Advanced WordPress Theme Editor vs Simple Editor Control