Just summing up my experience here because probably it helps some other ppl out:
A composer selfupdate works for me only with specifying a cache dir and the php binary I want to use (I have no write access outside my own web directory) COMPOSER_CACHE_DIR=./cmptmp /opt/bin/php56/php composer.phar --selfupdate
I had a flow error where nothing was displayed, also not in the logs, what did help was using /opt/bin/php56/php -d display_errors [theflowcommand]
When trying to do database related operations with flow (setcharset, migrate) I got an error Exception #1 in line 255 of /Data/Temporary/Development/Cache/Code/Flow_Object_Classes/TYPO3_Flow_Command_HelpCommandController.php: Catchable Fatal Error: Argument 1 passed to TYPO3\Flow\Command\HelpCommandController_Original::errorCommand() must be an instance of TYPO3\Flow\Mvc\Exception\CommandException, none given - I was unable to find any further information on this problem - what did help in the end was setting the php version to 7 in Configuration/Settings.yaml and also using the PHP7 binary in the commandline via /opt/php7/bin/php etc. - I had to put this back to 5.6 AFTER using the flow commands due to the fact that I don’t have a working imagick version for PHP7 on my shared host atm
Neos is a bit bold at PHP requirements and look like your shared host setup is bit messy. When the PHP binary is not in standard location, Flow can be a bit lost. You can help Flow by setting phpBinaryPathAndFilename
Not really related to Flow, look like composer is unable to create the ~/.composer in your ssh user home directory.
I say before that the PHP configuration look like a mess … and this is a symptom look like the PHP CLI share the same configuration has the PHP FPM / MOD_PHP … It’s important to not display error on web request but pretty important to show them on CLI.
Maybe we should create a command flow setup:check that can detect things like this, but has every shared hoster tent to have exotic configuration it should be hard to build something really useful
I think we need to give more documentation on setup requirements for Flow, and for my project I try to stay away of shared hosting (and not only for Flow/Neos) as much as possible.