composer update/require slow when enable XDebug in CLI environment

Recently I find there will be some issue to use composer command, which seems too slow to finish.

After my investigation, I find that this problem is often related to xdebug lodaed (doesn't matter if enabled or not) in my CLI environment.

We can check wether xdebug is enabled for CLI using:

// unix
php -m | grep xdebug

Solution:

Further information what operations take so long can be gained by enabling maximum verbosity and profiling information:

composer install --prefer-dist -vvv --profile

or

composer update --prefer-dist -vvv --profile

finally I run the command which worked:

composer require barryvdh/laravel-debugbar --dev --ignore-platform-reqs  -vvv --profile

refer to: https://getcomposer.org/doc/03-cli.md#update