拒绝用户“[myusername]”@“%”访问数据库“[mydbname]”
MySQL权限是细粒度的：并非所有用户都具有对服务器上所有数据库的完全访问权限。
您需要以管理员和grant the appropriate permissions的身份登录。例如，要授予完全访问权限：

GRANT ALL
ON mydbname.*
TO 'myusername'@'%'
WITH GRANT OPTION;
FLUSH PRIVILEGES;

...或者您可以根据自己的喜好进行选择：

GRANT SELECT, ALTER, CREATE, DELETE, DROP, INDEX, INSERT, REFERENCES, TRIGGER, UPDATE
ON mydbname.*
TO 'myusername'@'%';
FLUSH PRIVILEGES;

请查看Privileges Supported by MySQL以获取完整列表。
%是一个通配符，在帐户名和密码中详细解释，表示“从任何主机连接”。

我在xampp上也遇到过类似的问题。我把我的密码改为自动生成密码（通过生成密码按钮），然后复制粘贴到配置文件中。工作成功！

代码：

// config information
require_once "config.php";

// make connection string
$connection_string = "mysql:host=" . DB_HOST . ":" . DB_PORT . ";dbname=" . DB_NAME;
$connection = null;

// show connection string
echo $connection_string."</br>";

// try to connect to db or catch exceptions
try{
    $connection = new PDO( $connection_string, DB_USER, DB_PASS );
}catch (PDOException $exc){
    echo '<pre>';
    print_r($exc);
    echo '</pre>';
}

echo '</br>';

// connection status
if ( $connection ) {
    echo "Connected Successfully!";
} else {
    echo "Connection Failed!";
}

结果：

mysql:host=127.0.0.1:3306;dbname=php_pdo_db

Connected Successfully!

在PDO查询中，在主机之后添加端口（在我的例子中，将端口更改为8111），它应该可以工作。

• • 代码：**

//write in database
try {
    $dbh = new PDO("mysql:host=$db_host:8111;dbname=$db_name", $db_user, $db_password);
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $dbh->exec($database);
}
catch(PDOException $e) {
    if ($e->getCode() == 2002) {
        header('location: step3.php?_error=Unable to Connect Database, Please make sure Host info is correct and try again !');
        exit;
    }
    elseif ($e->getCode() == 1045) {
        header('location: step3.php?_error=Unable to Connect Database, Please make sure database username and password is correct and try again !');
        exit;
    }
    elseif ($e->getCode() == 1049) {
        header('location: step3.php?_error=Unable to Connect Database, Please make sure database name is correct and try again !');
        exit;
    }
}