Wordpress error establishing a database connection
First create testconn.php Fill it with the actual db connection string from either wp-config.php or from the client himself.
=======
<?php
$link = mysql_connect('localhost', 'root', 'password');
if (!$link) {
die('Could not connect: ' . mysql_error());
}
echo 'Connected successfully';
mysql_close($link);
?>
========
e.g.
http://www.domain.com/testconn.php
IF the error shows as :
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Could not connect: mysqlnd cannot connect to MySQL 4.1+ using the old insecure authentication. Please use an administration tool to reset your password with the command SET PASSWORD = PASSWORD('your_existing_password'). This will store a new, and more secure, hash value in mysql.user. If this user is used in other scripts executed by PHP 5.2 or earlier you might need to remove the old-passwords flag from your my.cnf file
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You have to reset the password for the mysql user to at 10+ alphanumeric characters e.g. for this client I reset the password to v6dkUd26PbR4w on mysql server I adjusted with following command, furthermore also updated wp-config.php accordingly.
mysql> UPDATE mysql.user SET Password = PASSWORD('v6dkUd26PbR4w') WHERE user = 'testdbuser_wp';
Query OK, 1 row affected (0.01 sec)
Rows matched: 2 Changed: 1 Warnings: 0
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.02 sec)
Finally feel free to remove, http://domain.com/testconn.php if you want.