In system installed phalcon 3.0 from distro.
composer install PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/phalcon.so' - /usr/lib/php/20151012/phalcon.so: cannot open shared object file: No such file or directory in Unknown on line 0 Loading composer repositories with package information Updating dependencies (including require-dev) Your requirements could not be resolved to an installable set of packages. Problem 1 - The requested PHP extension ext-phalcon >=3.0.0 is missing from your system. Install or enable PHP's phalcon extension.
After remote phalcon from require insstalation was finished. This is bug of composer or phalcon?