WP CLI “Error establishing a database connection” in localhost (MAMP)

Question

I get this error when I try to create something with WP CLI:

Error establishing a database connection. This either means that the username and password information in your `wp-config.php` file is incorrect or we can’t contact the database server at `localhost`. This could mean your host’s database server is down.

But I can open the site with the link: http://localhost:8888/projectname

Any idea?

Answer 1

Go into your wp-config.php and change your DB_HOST to 127.0.0.1 instead of localhost.

Credit goes to Craig Wayne above in the comments.

Answer 2

Step1: check if your mysql server is running Step2: if yes then you can log in to mysql using

mysql -u root -p

then enter your password: ( you must use this command from terminal ) then use following command to ensure that database exists:

show databases;
grant all privileges on database_name.* to 'root'@'localhost' identified by 'password';
flush privileges;
exit;

now edit the wp-config.php file and search for

define('DB_NAME', 'db_name');
define('DB_USER', 'root');
define('DB_PASSWORD', 'password');
define('DB_HOST', 'localhost');

Now restart the server and try to login to your wordpress dashboard. I hope it helps.

Answer 3

In my case, besides the aforementioned error message, I also got the warnings below:

PHP Warning:  mysqli_real_connect(): Server sent charset (255) unknown to the client. Please, report to the developers in /var/www/html/wp-includes/wp-db.php on line 1531
Warning: mysqli_real_connect(): Server sent charset (255) unknown to the client. Please, report to the developers in /var/www/html/wp-includes/wp-db.php on line 1531
PHP Warning:  mysqli_real_connect(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers in /var/www/html/wp-includes/wp-db.php on line 1531
Warning: mysqli_real_connect(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers in /var/www/html/wp-includes/wp-db.php on line 1531
PHP Deprecated:  mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in /var/www/html/wp-includes/wp-db.php on line 1562
Deprecated: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in /var/www/html/wp-includes/wp-db.php on line 1562
PHP Warning:  mysql_connect(): Server sent charset (255) unknown to the client. Please, report to the developers in /var/www/html/wp-includes/wp-db.php on line 1562
Warning: mysql_connect(): Server sent charset (255) unknown to the client. Please, report to the developers in /var/www/html/wp-includes/wp-db.php on line 1562
PHP Warning:  mysql_connect(): Server sent charset unknown to the client. Please, report to the developers in /var/www/html/wp-includes/wp-db.php on line 1562
Warning: mysql_connect(): Server sent charset unknown to the client. Please, report to the developers in /var/www/html/wp-includes/wp-db.php on line 1562

According to this question, this issue happens because the default charset for MySQL 8.0 is utfmb4.

In fact, I could replicate the error by upgrading from MySQL 5.7 to MySQL 8.0

I solved the issue by exporting the database, downgrading to MySQL 5.7 and re-importing the data. I also ran tests on MariaDB 10.3 and it works fine.