ERR_EMPTY_RESPONSE when debugging ionCube encoded php file with xdebug - php

Question

When I try to debug something inside vagrant, I can step through the code, the debugger stops at breakpoint and all looks fine, until the request is done. Then I get the following error in the browser: 324 ERR_EMPTY_RESPONSE. Usual requests (without xdebug) are working without any problem. I can also debug simple php-scripts without encoded content (we use ionCube).
Here are some infos:
vagrant#localdev:~$ php -v
PHP 5.6.36-1+ubuntu14.04.1+deb.sury.org+1 (cli)
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
with the ionCube PHP Loader (enabled) + Intrusion Protection from ioncube24.com (unconfigured) v6.0.6, Copyright (c) 2002-2016, by ionCube Ltd.
with Xdebug v2.5.5, Copyright (c) 2002-2017, by Derick Rethans
vagrant#localdev:~$ php --ini | grep -C20 'xdebug'
/etc/php/5.6/cli/conf.d/20-intl.ini,
/etc/php/5.6/cli/conf.d/20-ioncube.ini,
/etc/php/5.6/cli/conf.d/20-json.ini,
/etc/php/5.6/cli/conf.d/20-mbstring.ini,
/etc/php/5.6/cli/conf.d/20-mcrypt.ini,
/etc/php/5.6/cli/conf.d/20-mysql.ini,
/etc/php/5.6/cli/conf.d/20-mysqli.ini,
/etc/php/5.6/cli/conf.d/20-pdo_mysql.ini,
/etc/php/5.6/cli/conf.d/20-phar.ini,
/etc/php/5.6/cli/conf.d/20-posix.ini,
/etc/php/5.6/cli/conf.d/20-readline.ini,
/etc/php/5.6/cli/conf.d/20-shmop.ini,
/etc/php/5.6/cli/conf.d/20-simplexml.ini,
/etc/php/5.6/cli/conf.d/20-soap.ini,
/etc/php/5.6/cli/conf.d/20-sockets.ini,
/etc/php/5.6/cli/conf.d/20-sysvmsg.ini,
/etc/php/5.6/cli/conf.d/20-sysvsem.ini,
/etc/php/5.6/cli/conf.d/20-sysvshm.ini,
/etc/php/5.6/cli/conf.d/20-tokenizer.ini,
/etc/php/5.6/cli/conf.d/20-wddx.ini,
/etc/php/5.6/cli/conf.d/20-xdebug.ini,
/etc/php/5.6/cli/conf.d/20-xmlreader.ini,
/etc/php/5.6/cli/conf.d/20-xmlwriter.ini,
/etc/php/5.6/cli/conf.d/20-xsl.ini
vagrant#localdev:~$ cat /etc/php/5.6/cli/conf.d/20-xdebug.ini
zend_extension=xdebug.so
xdebug.remote_enable=On
xdebug.remote_host=192.168.123.1
; xdebug.remote_autostart=On
; xdebug.remote_connect_back=On
; xdebug.remote_handler="dbgp"
; xdebug.remote_port=9000
; xdebug.max_nesting_level=250
; xdebug.idekey="PHPStorm
I have the exact same issue as described here: https://intellij-support.jetbrains.com/hc/en-us/community/posts/206368089-Xdebug-only-partially-works
The last comment was:
After upgraded xdebug to 2.2.1 it's work fine for me :)
But I already use 2.5.5 and I think the problem is somehow related to IonCube.
I've read this, too, but as far as I see xdebug is loaded after ionCube anyway in my setup.