Creating a custom content-type.

You'll commonly see the empty pages referred to as WSOD (White Screen of Death). They are caused by any number of hundreds of possible errors in your code, so tracking down what is wrong requires some effort...

I use three things to help me debug:

1) I've installed xdebug for my local machine's php, which gives be a "traceback" dump of the function call stack when an error occurs.

2) I use this routine to place debug messages into a log file, with messages like "here 0", "here 1" and so on throughout the code to identify what logic is about to be called. When I've added log messages "here 0" thru "here 25", and the log stops at "here 16", I know the error is somewhere between "here 16" and "here 17".

function _dbgReport( $msg )
{
  $msg = $msg . "\n";
  file_put_contents( '/path/to/log/drupal_debugging_log.txt', $msg, FILE_APPEND );
}

3) I've downloaded and made a local version of this site: http://www.meandeviation.com/tutorials/learnphp/php-syntax-check/ (see the download link middle of the page). This allows me to check my module code for php syntax errors before attempting to run it. I use it every time I've made edits to the php. You get surprized how many simple errors you can make, expecially if you often work in multiple programming languages.

Note that I've wasted around 12-14 hours trying to get the Komodo IDE to work, which claims the ability to single step through php, even on a remote server. Trying to set that up is how I got xdebug installed on my machine. However, unless they make radical improvements to their documentation, I don't recommend trying to get Komodo IDE to work, it's a Time Vampire. I gave up on it.