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Symptom

You're using a PHP code similar to this:

$hostname = 'localhost:3306';
$username = 'cu-loginname01_user01';
$password = 'Dbng%3r92';
$dbname = 'cu-loginname01_db01';
$db = mysqli_connect($hostname, $username, $password, $dbname) or die('login failed');

You are sure that the database login name and database password are correct. Nevertheless no login succeeds.

Cause

The database differentiates between host name and port. If you give a user permission to access the host "localhost", it is different than if it is called "localhost:3306". The database does not know a suitable user data record for “localhost:3306”.

Solution

Omit the port specification. If you want to specify a port, this must at least be passed separately as a port to the PHP mysqli_connect() function. The correct PHP code for the example would be:

$hostname = 'localhost';
$port = '3306';
$username = 'cu-loginname01_user01';
$password = 'Dbng%3r92';
$dbname = 'cu-loginname01_db01';
$db = mysqli_connect($hostname, $username, $password, $dbname, $port) or die('login failed');

or

$hostname = 'localhost';
$username = 'cu-loginname01_user01';
$password = 'Dbng%3r92';
$dbname = 'cu-loginname01_db01';
$db = mysqli_connect($hostname, $username, $dbname, $password) or die('login failed');

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