Error MySQLへの接続失敗

MySQLサーバへの接続が確認できません。

SQLSTATE[HY000] [2002] Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

array(1) {
  [0]=>
  array(7) {
    ["file"]=>
    string(41) "/usr/home/mw2psc506w/www/htdocs/index.php"
    ["line"]=>
    int(27)
    ["function"]=>
    string(11) "__construct"
    ["class"]=>
    string(17) "Qrt\Core\Quartett"
    ["object"]=>
    object(Qrt\Core\Quartett)#1 (0) {
    }
    ["type"]=>
    string(2) "->"
    ["args"]=>
    array(0) {
    }
  }
}