WP Plugin: “Syntax Highlighter for WP Editor”
An easy to use WordPress plugin that replaces the default Theme and Plugin Source Code Editor with an enhanced editor by a CodeMirror library. The WordPress default Theme Editor (in Appearance => Editor) and Plugin Editor (in Plugins => Editor) is great for doing some custom changes to your Themes or Plugins files, although it is rather limited. This is where the “Syntax Highlighter for WP Editor” can help. With an enhanced source code editor you can see a code with syntax highlighting, and with line numbering, so you can easily read your code and detect any errors.