How to downgrade php xdebug version

I also face same problem today. Here is how I solve this:

remove xdebug 3.0.1 first

sudo apt purge php-xdebug
sudo apt remove php-xdebug

Prerequisit:

sudo apt install php7.2-dev

Now clone xdebug repo and compiled:

git clone git://github.com/xdebug/xdebug.git
git checkout xdebug_2_9
phpize
./configure --enable-xdebug
sudo make install
sudo service apache2 restart

Now add following to your php.ini

zend_extension=xdebug.so
xdebug.remote_enable=1
xdebug.remote_port=9000

Best of luck!

If you're on PHP 7.1 then you have to execute the following

apt-get install php-all-dev
git clone --branch xdebug_2_9 --single-branch git://github.com/xdebug/xdebug.git
cd xdebug
phpize7.1
./configure --enable-xdebug
make
make install
phpenmod xdebug
echo "zend_extension=/usr/lib/php/20160303/xdebug.so" > /etc/php/7.1/mods-available/xdebug.ini