Here is a simple Web 1.5 (static HTML with a little bit of styling and JavaScript) recipe to allow a viewer of your web page to see the PHP source-code, behind it, with a minimal amount of JavaScript and a little CSS manipulation—good for showing the work you’ve done to others. Or for embedding in your own source, in debug mode, so that teammates can see each others’ work.
See the example code at: http://cachecrew.com/sample_code/highlight_file.php and http://cachecrew.com//sample_code/highlight_file2.php.