Warning: mysql_connect(): Access denied for user: 'testuser4@localhost' (Using password: YES) in /usr/local/apache2/htdocs/test/db_conn_test.php on line 3

<?php
/* Verbindungsaufbau zum Datenbankserver */
$link = mysql_connect('localhost', 'testuser4', 'testuser4')
   or die('Verbindungsaufbau fehlgeschlagen : ' . mysql_error($link));

mysql_select_db('test', $link)
   or die('Konnte die Datenbank nicht auswählen');

/* SQL Abfrage senden */
$query = 'SELECT * FROM testtable';
$result = mysql_query($query, $link) or die('Abfrage fehlgeschlagen : ' . mysql_error($link));

while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) {

   foreach ($row as $col_value) {
       echo "\t\t$col_value\n";
   }

}

/* Speicher wieder freigeben */
mysql_free_result($result);

/* Verbindung schliessen */
mysql_close($link);
?>

insert into user values('localhost', 'testuser1', '');
grant all privileges on test.* to testuser1;

mysql_connect('localhost', 'testuser1', '') ....

insert into user values('localhost', 'testuser2', 'testuser2');
grant all privileges on test.* to testuser2;

mysql_connect('localhost', 'testuser2', 'testuser2') ....

insert into user values('localhost', 'testuser2', PASSWORD('testuser2'));
grant all privileges on test.* to testuser2;