How to use phpPgAdmin with Postgres
Your setup if fine except for pg_hba.conf which lacks an entry for 192.168.7.4.
Consider adding it and reload the postgresql service:
host all all 192.168.7.4/32 md5
I tried the above solution but still got the 'Login Failed' message. To resolve, I had to ensure IPv6 is set to password in the pg_hba.conf file. So do: vi /var/lib/pgsql/9.4/data/pg_hba.conf and edit accordingly. Then restart both httpd & postgresql (whatever the version you are using)