PHP 无法连接到 MySQL 服务器

Question

I have a few PHP servers connecting to my MySQL server through my DNS redirect and the code is a normal mysqli-connection:

$db_link = mysqli_connect(server, user, passwort, database, port);

2 PHP servers can access the MySQL with this script, 2 can't and I have no idea where to search for the mistake in my system as they are running different Linux OS and PHP versions (5.3-5.8).

Error message:

Can't connect to MySQL server on 'servername' (111)

As two of them can connect through the DNS host, I think the MySQL and DNS server shouldn't be a problem.

Has anyone an idea where the problem could be?

Answer 1

Basic reasons:

• There is no MySQL server running at the specified host

• Connection to the MySQL server is not allowed using TCP-IP. Check the 'skip-networking' setting in the MySQL configuration file (my.ini on Windows, my.cnf on Unix/Linux). It shall be commented out like '#skip-networking'. If it is not commented out, then do it and restart the MySQL server for the change to take effect. SQLyog needs to connect using TCP-IP.

• Some networking issue prevents connection. It could be a network malconfiguration or a firewall issue. We have experienced sometimes that some firewalls (ZoneAlarm in particular) is blocking TCP-IP connections even if it claims to be disabled. Most often it will help to uninstall and reinstall the firewall.

• When trying to connect to a MySQL server at an ISP this error message often indicates that direct connection to MySQL has been blocked. You must then use HTTP-tunneling or SSH-tunneling to connect.

• Also this FAQ may have relevant information. It describes some more special situations when connection to MySQL on Linux

http://faq.webyog.com/content/23/15/en/error-no-2003-can_t-connect.html