如何从这个多维数组中形成JSON

Question

My query returns the following:

post_id    post_type    post_text
1          text         bla1
2          pic          bla2
3          text         bla3

I loop through this result as follows:

$posts = array();
foreach ($query->result() as $row) {
    $post = array();
    $post['post_id']         = $row->post_id;
    $post['post_type']       = $row->post_type;
    $post['post_text']       = $row->post_text;
    $posts[] = $post;
}
$data['posts'] = $posts;

return $data;

If I json_encode and output from my controller I get this:

{
    "stream": {
        "posts": [{
            "post_id": "1",
            "post_type": "text",
            "post_text": "bla1",
        },
        {
            "post_id": "2",
            "post_type": "pic",
            "post_text": "bla2",
        },
        {
            "post_id": "3",
            "post_type": "text",
            "post_text": "bla3",            
        }]
    }
}

However if a post has comments, my query returns

post_id    post_type    post_text    comment_id    comment_text
1          text         bla1         7             asd
1          text         bla1         8             sdf
2          pic          bla2
3          text         bla3         10            rty
3          text         bla3         11            yuo

How should I set up the foreach loop to build an array that will output JSON like this?

{
    "stream": {
        "posts": [{
            "post_id": "1",
            "post_type": "text",
            "post_text": "bla1",
            "comment": [{
                "comment_id": "7",
                "comment_text": "asd",
            },
            {
                "comment_id": "8",
                "comment_text": "sdf",
            }],
        },
        {
            "post_id": "2",
            "post_type": "pic",
            "post_text": "bla2",
        },
        {
            "post_id": "3",
            "post_type": "text",
            "post_text": "bla3",            
            "comment": [{
                "comment_id": "10",
                "comment_text": "rty",
            },
            {
                "comment_id": "11",
                "comment_text": "yuo",
            }],
        }]
    }
}

This JSON is consumed on Secha framework as follows:

                    proxy: {
                        type: 'jsonp',
                        url: 'http://myurl',
                        reader: {
                            type: 'json',
                            rootProperty: 'stream.posts'
                        }
                    }

Answer 1

Although I prefer to query each post individually for the existence of comments, here would be one attempt to construct the array using one query.

$posts=array();
$data = array();
foreach($query->result() as $row){
  // if the post hasn't been created in the array
  // create it
  if(!isset($posts[$row['post_id']])){
    $posts[$row['post_id']] = array(
      "post_type" => $row['post_type'],
      "post_text" => $row['post_text']
    );
  }
  // if a comment is found
  if(isset($row['comment_id'])){
    $posts[$row['post_id']]['comments'][] = array(
      "comment_id" => $row['comment_id'];
      "comment_text" => $row['comment_text'];
    );
  }

}
$data['posts'] = $posts;

JSON encoding this array would create something like...

{ "posts" :
   {
     1 : {
       "post_type" : "something",
       "post_text" : "something else"
     },
     2 : {
       "post_type" : "something",
       "post_text" : "something else",
       "comments" : [
         {"comment_id":1,"comment_text":"something"},
         {"comment_id":2,"comment_text":"something"}
       ]
     },
    ....
   }
 }

I cant vouch for this code completely working as I haven't tested it, but it should be a start. Again, if I were you I'd just query each post individually.

Answer 2

I don't know PHP syntax so I wont write the code. However this is not a PHP problem, but an algorithm problem.

What you could do to handle this data is doing it in three steps, with a intermediate result that would be a dictionary of posts. In this dictionary, keys will be post ids, and values will be posts.

1/ Iterate over the lines returned by your query. For each of this lines, check if the post involved in this line exists in the dictionary. No -> Add a new post object. Yes -> Just add the comment to the existing post object.

2/ Iterate through your dictionary to add each post contained in it to an array.

3/ Sort your array by the id of the post (here i'm assuming that the id is in the same order as the posts, but just a little advice: you should probably have a post date and sort by post date).

If you master PHP syntax, your should be able to implement it easily. Don't hesitate to submit an edit if you know the PHP syntax for this.

I hope this helps.

Answer 3

This code

    foreach($query->result() as $row){
      // if the post hasn't been created in the array
      // create it
        if(!isset($post[$row->post_id])){
            $post[$row->post_id] = array(
              "post_id" => $row->post_id,
              "post_text" => $row->post_text
            );
        }
        // if a comment is found
        if(isset($row->comment_id)){
            $post[$row->post_id]['comments'][] = array(
              "comment_id" => $row->comment_id,
              "comment_text" => $row->comment_text
            );
        }
    }

    return $posts[] = array_values($post);

returns this (what I need):

   [
     {
       "post_id"   : "something",
       "post_text" : "something else"
     },
     {
       "post_id"   : "something",
       "post_text" : "something else",
       "comments" : [
         {"comment_id":1,"comment_text":"something"},
         {"comment_id":2,"comment_text":"something"}
       ]
     },
    ....
   ]