This is expected behaviour. If you create a infinite recursion than PHP can run out of stack space, which it does here. In most situations when Xdebug is not loaded, you run out of normal system memory before this stack overflow happens, which is why you wouldn't see it without xdebug loaded in most cases.

There is a workaround though, through Xdebug's develop mode. If you set xdebug.mode=develop,debug, the result of this will be an error like:

Fatal error: Uncaught Error: Xdebug has detected a possible infinite loop, and aborted your script with a stack depth of '256' frames in Standard input code on line 4

Error: Xdebug has detected a possible infinite loop, and aborted your script with a stack depth of '256' frames in Standard input code on line 4

Call Stack:
    7.6736     439624   1. {main}() Standard input code:0
    7.6736     439624   2. callMe() Standard input code:7
…

Which should then give a good hint as to how to fix your code.