If you have ever tried to display code within a post you will know all about the problems this can cause. That is why there are some amazing developers who create plugins to make that solve this niggly issue.
Which is the best? I have been using Code Markup, it is simple to use and displays the code just the way I wanted it. To be honest, they are all good, it just depends on your needs.
Make sure that the WYSIWYG editor is disabled, in most cases these plugins will not work with these types of plugins.
Some plugins haven’t been tested all the way up to version 2.7 but,the chances are that they will work.
Plugin URL : WP Advanced Code Editor.
Description : WP Advanced Code Editor integrates the EasyArea advanced code editor into wordpress. This adds real time syntax highlighting, line numbering, full screen editing, and more to the code editor in the “Add New Post” and “Add New Page” screens.
WP Compatibility : 2.3 – 2.7.
Note : Make sure that the WYSIWYG editor is disabled, the plugin is not compatible with the WYSIWYG editor.
WP Advanced Code Editor Screenshot (Admin View)