ftp passive mode and php

I have an Apache web server running on this machine with Debian stable, this PHP program have to connect using FTP to a remote online server among other things.

Everything worked fine until I installed an FTP server (vsftpd version 3.0.3-8+b1), but I don't think this is the culprit.

Now I get this error

The exact error/s are:

I won't open a connection to x.x.x.x --->*remote server ip* (only to x.x.x.x ---->*my public ip*)

And can't even ls remote directories, getting this error instead:

Unable to list directory

I suspect this is because FTP runs in active mode "by default" now, but I am really not sure. Those errors seems something related with passive mode.

What do you think?

• Debian version: Debian GNU/Linux 9
• PHP version: 7.0.30-0+deb9u1

The PHP routines we are talking about are: ftp_login() and ftp_fput()

I think it's auto active mode because everytime I use ftp_pasv(, true) it does work fine. Didn't have to specify before.