What to do if the connection between php and mysql fails

PHP is a popular programming language that is closely related to MySQL. Creating a valid PHP and MySQL connection is very important for developers. However, there are issues with connection failures, which can frustrate developers. This article will provide an in-depth understanding of why php and mysql connection failures occur and provide you with solutions.

1. Possible reasons

1. MySQL service is not running normally
   There may be a problem with the MySQL service, resulting in the inability to connect. You can check whether the MySQL service is running with the following command.

sudo service mysql status

2. Port problem
   MySQL default port is 3306. Make sure your code and MySQL port match. If your MySQL runs on a different port, you need to specify the port explicitly in your code.
3. Incorrect username and password
   If the username and password are incorrect, the connection will not be established. This is a very common problem and it is very important to check that the username and password are correct.
4. The problem of setting the host name
   When connecting to MySQL, the host name is also very important. You can use localhost or specify an IP address. If the connection fails, check that the hostname is correct.

2. Solution

1. Check MySQL service status
   If the MySQL service is stopped, the connection cannot be used. You can check the status of the MySQL service with the following command:

sudo service mysql start

If MySQL is not running, start it with the following command:

sudo service mysql start

2. Check the MySQL port number
   After upgrading the MySQL version, you may want to change the port number. Make sure the port number is correct and update the code.
3. Check username and password
   Please make sure the username and password are correct and paired with the MySQL server. Otherwise, the MySQL server cannot be connected.
4. Check the host name
   The host name is also very important, you can use localhost or specify the IP address. If your hostname is incorrect, the MySQL connection cannot be established.
5. Check Firewall Settings
   If a firewall is set up, the connection may be blocked. Allow ports that allow MySQL connections through the firewall.

sudo ufw allow 3306/tcp

The above are several methods to solve PHP and MySQL connection failure. Troubleshoot and resolve issues by checking the MySQL service status, port, username and password, and hostname, and checking firewall settings.

In short, PHP and MySQL are a very important technology combination, which plays an important role whether in web development or other fields. If you are experiencing MySQL and PHP connection issues, please use the above methods to resolve the issue.

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