Finding out the culprit #
You are free to choose the tool to find out the problem. Not to mention that it must identify the problem within the deadline.
We recommend using xdebug
to find the issue. It is effective in situations when you are not able to print the variables on the page. Like, in the case of AJAX callbacks. We understand that it doesn’t work out of the box and needs an IDE setup. We believe it is worth investing time to do the setup because it pays out well in the long run.