Here's the things that I encountered.

1. includes/db/connect_db_mysqli.inc
    I did not have mysqli setup correctly in the php.ini
    It took a while to find.... I think it would be helpful to put a
    try / catch around the mysql_connect call..
e.g.

function db_create_db($connection)
{
        global $db;

try {

        $db = mysqli_connect($connection["host"], $connection["dbuser"], $conne\
ction["dbpassword"], "",
                !empty($connection["port"]) ? $connection["port"] : 3306); // d\
efault port in mysql is 3306

}
catch(Exception $err)
{
        echo $err->getMessage();
}

}

/// end code

at least then there is a message that shows up when you attempt to install

2. I ran into the gettext code isssue where the language is set to C

3. when I installed the restapi - the whole process got a whole lot harder....
    The system was not returning data at all.....

    It turns out that the function get_magic_quotes_gpc doesn't exist in php 8.....

    The version of the api has Slim code that you have has that in Slim/Http/Request.php
    and also its in session-util.inc

    Definitely there should be some code like...
   if (function_exists("get_magic_quotes_gpc"))
      .......
    The disturbing thing is that the code dies without any kind of logging....... when it hits get_magic_quotes_gpc.
   
4. an observation....
      it seems like the frontaccount software should ship with the restapi module by default....
     its difficult to figure out the restapi version stuff... it would make more sense if it just was in one tar ball...
     I suspect fabridge should also be that....     But the obvservation is just my two cents - I'm sure there's
a rational for it to be broken up as it is.

Cheers,