How to fix PHP error "Maximum function nesting level of '100' reached" in WordPress ?

That is an error generated by xdebug extension for PHP. You can disable the setting as documented here: xdebug.max_nesting_level.

WordPress offers a simple way to fix this problem. Simply add the following line of code in your wp_config.php file and set a value higher than 100 :

	ini_set('xdebug.max_nesting_level', "500");