修改访问地址为：api.test.com/users

'urlManager' => [
    'enablePrettyUrl' => true,
    //'enableStrictParsing' => true,
    'showScriptName' => false,
    'rules' => [
        ['class' => 'yii\rest\UrlRule', 'controller' => 'user'],
    ],
]

上面是对路由进行美化，可以理解为去掉'index.php'