LEFT JOIN 关联查询的时候，关联表的字段原来是整型的，查出来就变成字符串了 [ 2.0 版本 ]

'components' => [
    'db' => [
        'class' => 'yii\db\Connection',
        'dsn' => '',
        'username' => '',
        'password' => '',
        'charset' => '',
        'attributes' => [   //把这个attributes加一下 
            PDO::ATTR_STRINGIFY_FETCHES => false,
            PDO::ATTR_EMULATE_PREPARES => false,
        ]
    ],
    ]