Require_once问题，当调用包含在另一个文件中的函数时

我的问题是:

index . php内容:

require_once('phpcommonscripts/connections/connection.php');
require_once('phpcommonscripts/functions/logging.php');
    Func_LogToDB($logType, $actionType, $errMsg, $varUser);

connection.php内容:

$hostname_MYDB = "localhost";
$database_MYDB = "MYDB";
$username_MYDB = "USER";
$password_MYDB = "PASS";
$MYDB = mysql_pconnect($hostname_MYDB, $username_MYDB, $password_MYDB) or trigger_error(mysql_error(), E_USER_ERROR);

logging.php内容:

function Func_LogToDB($lType, $lAction, $lMessage, $lUser) {       
    mysql_select_db($database_MYDB, $MYDB);
}

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错误信息:

注意:未定义变量:database_MYDB在/home/notes/public_html/phpcommonscripts/functions/logging.php第22行

(第22行是mysql_select_db()行…)

我做错了什么吗?