Why Does mysqli_connect() Fail with 'Authentication Method Unknown (Caching_sha2_password)'?

mysqli_connect: Authentication Method Unknown (Caching_sha2_password)

Background:

When using MySQL's mysqli_connect() function, an error can arise: "error: mysqli_connect(): The server requested authentication method unknown to the client." This indicates a mismatch between the authentication method used by the server and that implemented by the client.

Specifically, if the MySQL server is set to use the caching_sha2_password authentication method, the error can occur when the client does not support or is not configured to use that method.

Troubleshooting and Solution:

In the given case, the MySQL Server is configured to use caching_sha2_password authentication, which the PHP client is not equipped to handle. To resolve this issue, you can:

1. Modify MySQL Server Configuration:

Change the default_authentication_plugin setting in MySQL's ini file (my.ini on Windows, /etc/my.cnf on Linux) from caching_sha2_password to mysql_native_password. This will allow the server to use the older authentication method.

2. Update PHP Client:

Upgrade the PHP MySQL client to a version that supports caching_sha2_password authentication. However, this may not be necessary, as the server configuration change should rectify the issue.

3. Set User Authentication:

Run the following SQL command in MySQL:

ALTER USER 'username'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password';

This command will alter the authentication method for the specified user to mysql_native_password, allowing them to connect despite the server's caching_sha2_password setting.

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