It happens often that I see an empty page where I would expect something. One example is when I migrate a server and have a php script running on a new server. It may turn out that this new server does not have a specific PHP module and that is why it does not work. Similarly, if I forget a ";" at the end of a command, the whole php file will just show nothing in the browser.
Here is a php trick that outputs debugging output when you want.
$handler=fopen("/tmp/debug","a"); fwrite ($handler, "hello world"); fclose ($handler);
example for variables:
$handler=fopen("/tmp/debug","a"); fwrite ($handler, var_export($variable,true)); fclose ($handler);
To output an array use