函数commentdelete（）在php上

i want to make function for delete comments on my database. My database is Mongodb. So when i delete an account i want the comment of user also removes.

So for example I want to delete the account of Mark, I want these comments are also deleted.

This my database:

  { "_id" : ObjectId("55bd4ead0faaf25f05b7acd9"), "title" : "test", "content" : "test", "user" : "Mark", "saved_at" : ISODate("2015-08-01T22:56:45.465Z"), "comments" : [ { "comment" : "hello how are u ?", "user" : "Marc" }, { "comment" : "i'm fine and you", "user" : "Paul" } ] }

i have make this function commentdelete(), but the function does not work, the comments do not delete.

function commentdelete() {
    try{
        $connection = new MongoClient();
        $database = $connection->selectDB('blog');
    }Catch(MongoException $e){
        die("Failed to connect to database " . $e->getMessage());
    }

    $collection = $database->articles;
    $query=array();

    $cursor=$collection->find($query);

    $collection->update(
        [],
        ['$pull' => ['comments' => ['comment' => $_SESSION["user"]]]],
        ['multiple' => true]
    );
}

Thanks with the help

It looks like you are referencing the wrong field in your $pull. Should be "user":

$collection->update(
    [],
    ['$pull' => ['comments' => ['user' => $_SESSION["user"]]]],
    ['multiple' => true]
);

You have "comment", which would not seem to match the "session user" variable you are using.