Did you already tried to insert like this:
define('DB_HOST', 'your_host_ip:8889');
instead of localhost
Or could be a problem connection to your mysql server.
Create a new file like conn.php and write this:
<?php
$link = mysqli_connect("127.0.0.1", "my_user", "my_password", "my_db", "my_port");
if (!$link) {
echo "Error: Unable to connect to MySQL." . PHP_EOL;
echo "Debugging errno: " . mysqli_connect_errno() . PHP_EOL;
echo "Debugging error: " . mysqli_connect_error() . PHP_EOL;
exit;
}
echo "Success: A proper connection to MySQL was made! The my_db database is great." . PHP_EOL;
echo "Host information: " . mysqli_get_host_info($link) . PHP_EOL;
mysqli_close($link);
?>
– If connects successfully verify the user permissions and verify again your wp-config there is something wrong
– if you can’t connect, well is your server and probably you have to contact your host