If the command "php bin/magento list" does not return the list of all Magento 2 available commands (empty output). Same happens for other commands.

php  bin/magento  list 

Method 1:
Open bin/magento in your preferred file editor and add the following line and save:

ini_set('display_errors', 1);  // allow PHP errors reporting

Run the command again:

php  bin/magento  list

If you get Fatal error: Allowed memory size of x bytes exhausted (tried to allocate y bytes), then it is a memory issue. Increase the memory limit by adding the following line then save.

ini_set('memory_limit','800M'); 

Run the command again:

php  bin/magento  list

to see if it works.
Method 2:
add -d memory_limit=XX
example: php -d memory_limit=4G bin/magento setup:di:compile