In this new post to his site Joshua Thjissen has shared some of his discoveries with Xdebug, Symfony 2 and problems with maximum nesting levels of objects in his testing.

Here you are, developing your code based on the Symfony2 framework. Creating a form here, add a Twig template there, until suddenly, boom! Your site doesn’t work anymore, and all the info you can find in your PHP logs is [an error about the maximum function nesting level being reached.

[...] What just happened? Did I create some kind of recursive function I wasn’t aware of, did somebody commit code that I accidentally pulled? Fortunately for us developers, there is a quick way to deal with this: google it...

According to the information he found via his search it's a common issue and can be "fixed" by bumping up the max_nesting_level to a higher value. He could have stopped there but he wanted to explain why this problem happened, what the nesting is all about, how it relates to the limitations of XDebug and why Twig could cause problems with it.