local server can't connect to remote postgresql database using PHP, but local terminal can connect

Question

The title might make this seem like a duplicate of some existing questions here on SO, but its kind of not in a way, in my opinion.

8140863 , 30617357 , 27749691

But I can't for the life of me make the answers to these threads work, instead of asking questions on those threads, I would like to create my own question, I'd like to discuss my setup and then my problem, and then what I've tried

My server setup is this, I have a local(an actual physical machine) and a VPS I'm renting, both are running at Centos7.x, PostgreSQL10, Php 7.x, and Python-2.x, BOTH can ping and ssh each other through a VPN just fine.

Both can connect to their own respective databases just fine through PHP, Python, PSQL Terminal

On my VPS Server, I can connect to my Local Server's PostgreSQL database using Python(psycopg2), PHP(php-pgsql) and Terminal(psql) totally fine.

On my local server, I can connect to my VPS PostgreSQL using Python(psycopg2) and Terminal(psql) EXCEPT through PHP(php-pgsql)

Whenever I connect to VPS's PostgreSQL through PHP, I'm getting this error like everyone else

pg_connect(): Unable to connect to PostgreSQL server: 
could not connect to server: Permission denied 
Is the server running on host "123.456.0.789" and accepting TCP/IP connections on port 5432?

Here are what I've done.

1. On postgresql.conf set listen_address = "*" -- this is OK
2. Added pg_hba entries for both -- this is OK (python and terminal can connect on both)
3. Port 5432/tcp is both enabled and allowed -- this is OK
4. Selinux is disabled -- this is the answers for the thread referenced above, but it doesn't work for me even after reboot of course.

these are the result of my netstat

#netstat -na | grep 5432
tcp        0      0 0.0.0.0:5432            0.0.0.0:*               LISTEN
tcp6       0      0 :::5432                 :::*                    LISTEN
tcp6       0     94 ::1:55110               ::1:5432                ESTABLISHED
tcp6       0      0 ::1:5432                ::1:55060               ESTABLISHED
tcp6       0      0 ::1:5432                ::1:55110               ESTABLISHED
tcp6      12      0 ::1:5432                ::1:55108               ESTABLISHED
tcp6       0     12 ::1:55108               ::1:5432                ESTABLISHED
tcp6       0      0 ::1:55060               ::1:5432                ESTABLISHED
unix  2      [ ACC ]     STREAM     LISTENING     31102    /var/run/postgresql/.s.PGSQL.5432
unix  2      [ ACC ]     STREAM     LISTENING     31104    /tmp/.s.PGSQL.5432

iptables

#iptables-save | grep 5432
-A IN_public_allow -p tcp -m tcp --dport 5432 -m conntrack --ctstate NEW,UNTRACKED -j ACCEPT

getenforce

#getenforce    
Disabled

Selinux

#/usr/sbin/sestatus | grep SELinux
SELinux status:                 disabled
#sudo setsebool -P httpd_can_network_connect_db 1
setsebool:  SELinux is disabled.

postgresql.conf

listen_addresses = '*'                           
port = 5432   

pg_hba.conf (i just changed the ip for posting here) I tried using trust , but its still the same

# "local" is for Unix domain socket connections only
local   all             all                                     password
# IPv4 local connections:
host    all             all             127.0.0.1/32            password
host    all             all             123.456.0.1/32            password
host    all             all             123.456.0.11/32           password
host    all             all             123.456.0.20/32           password
# IPv6 local connections:
host    all             all             ::1/128                 password

edit start: My PHP pg_connect code (I just changed the IP just for this post, but it points to the VPS IP)

$pgcon = pg_connect("dbname=database1 user=some_user password=some_password host=123.456.0.789");

edit end: ==

I would like to emphasize that BOTH servers can connect on each others and their own PostgreSQL database through other means, with the exception of my Local Server, it couldn't connect to VPS PostgreSQL using PHP.

VPS To Self(localhost connection)

VPS to Self via PHP is OK
VPS to Self via Python is OK
VPS to Self via PSQL(Terminal) is OK

VPS To Local Server(Connecting using Local Server's VPN IP)

VPS to Local Server via PHP is OK
VPS to Local Server via Python is OK
VPS to Local Server via PSQL(Terminal) is OK

Local Server to Self(localhost connection)

Local Server to Self via PHP is OK
Local Server to Self via Python is OK
Local Server to Self via PSQL(Terminal) is OK

Local Server to VPS(Connecting using VPS's IP by VPN and Public IP)

Local Server to VPS via Python is OK
Local Server to VPS via PSQL(Terminal) is OK
Local Server to VPS via PHP Is NOT OK

I'm really sorry for the long thread, I wanted to give as much information as I can.

Answer 1

Let's split error by types. I'd made several tests with your case and what I found:

1. If we mess with connection parameters (ie wrong port, or IP address) we get the error "could not connect to server: Connection refused" or "Operation timed out Is the server running on host "128.0.0.1" and accepting")

2. If we mess with credentials, we get the error "FATAL: password authentication failed for user..."

3. Permission denied can be thrown only if you have not permissions to open a TCP connection from your PHP library.

Pls, double-check if you disable SElinux on your Local Server as for me, this is still the closest workaround for your problem.