Fatal error: Uncaught PDOException: SQLSTATE[08004] [1040] Too many connections in C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Connection.php:723 Stack trace: #0 C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Connection.php(723): PDO->__construct('mysql:host=127....', 'root', '123456', NULL) #1 C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Connection.php(638): yii\db\Connection->createPdoInstance() #2 C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Connection.php(1063): yii\db\Connection->open() #3 C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Connection.php(1050): yii\db\Connection->getMasterPdo() #4 C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Command.php(261): yii\db\Connection->getSlavePdo() #5 C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Command.php(1163): yii\db\Command->prepare(true) #6 C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Command.php(410): yii\db\Command->queryInternal('fetchAll', NULL) #7 C:\WebServerAliYun\Uioin\common\config\bootstrap.php(28): yii\db\Command->queryAll() #8 C:\WebServer in C:\WebServerAliYun\Uioin\vendor\yiisoft\yii2\db\Connection.php on line 649