对于路由，您必须在路由前添加@":url_for('@category_set_representative_image', array('sf_subject' => $类别))

for routes you will have to add "@" before the route: url_for('@category_set_representative_image', array('sf_subject' => $category))

你有routing.yml结尾的默认路由吗?

do you have you the default route at the end of the routing.yml?