Hi, all, I'm new to Flarum and having solved a few issues during installation I wanted to share in case the same scenario might help others.
First off, I'm using shared hosting (in the UK with UK2). Issue number 1 was in trying to install Composer. I had UK2 Support enable shell access so I could SSH in, but when running the Composer installer, I received an error that the php configuration had allow_url_fopen=Off and that option was required for dependencies to work properly. I checked my php.ini file and indeed it contains allow_url_fopen=On. Confused. It turns out that command line php (required to install Composer) uses a different php.ini file and as a shared hosting customer I do not get access to it. So, to get around this problem, I had to use the -d option to override php.ini settings:
#php -d allow_url_fopen=On composer-setup.php
This allowed the installer to run with allow_url_fopen set to to on.
Next problem, I discovered that Flarum has to be installed into an empty folder. So, it's impossible to use a local installation of Composer in the same folder as the folder into which Flarum in being installed. OK, so I installed Composer into its own folder, and then created a shiny new empty folder for Flarum. Of course I had to use the same syntax in the install, so for me the line that worked was:
php -d allow_url_fopen=On ../composer/composer.phar create-project flarum/flarum . --stability=beta
During install, I see a large number of errors reporting that "The Process class relies on proc_open, which is not available on your PHP installation." This is because proc_open is disabled on the command line php, but it is enabled within my php.ini which applied to my shared hosting, so this will in fact not be a problem.
I also see many occurrences of "Unzip with unzip command failed, falling back to ZipArchive class" which I guess must be a characteristic of my shared hosting. Doesn't seem to cause a problem.
OK, so having run the installer, I think I am on the home straight. I browse to http://mydomain.com/forum and see a 500 error. Looking at the apache error log, it reports "index.php is writeable by group" which is evidently forbidden by my shared hosting setup. So I CHMod index.php to 644, and reload the page.
Now I get the "Install Flarum" page, and I am able to set up my Flarum.
All Ok now until I try to go to "Administration" at which point I get another 500 error. This time the error log reports that "admin.php is writeable by group" so I CHmod that to 644 (from 664 as it had been after install).
Refresh the page, success. Everything running perfectly.
As you can imagine it took a while to get past all those issues, so I wanted to to report here so that (a) it might help someone in the same situation and (b) in case those working on the install script might want to know.