PHP升级后无法连接到外部Mysql

Using Ubuntu 16.10

I have been using external Mysql server just fine, but today I did an apt update and apt upgrade, after that. PHP simply won't connect to external mysql server anymore. I can connect the server via command line using mysql though, but php just does not. I tried simple script to open to connection and

mysqli_connect_error(); just gives out an error "connection refused"

Ports are open. Any idea why this suddenly happened after an update?

EDIT: Updated the client server. The server where external mysql is running works fine, I can connect to it from other servers. But one client server where php script runs can't access it after an update.

Found it. php 7 does not support ip:port anymore, but port has to be set up separately. Changed the default port via: ini_set('mysqli.default_port', 'port'); in the file where connection was made as I was unable to change it in the script I am using.