How can we get all array elements in Mongodb?

Question

I have a classroom collection structured as

{
  "_id" : ObjectId("517a54a69de5ee980b000003"),
  "class_name" : "A",
  "students" : [{
    "sname" : "John",
    "age" : "13"
  }, {
    "sname" : "Marry",
    "age" : "12"
  }, {
    "sname" : "Gora",
    "age" : "12"
  }]
}

With php, I like to get and list all students based on class _id . How can we do it?

UPDATE The query I use:

$student_list=$collection->find(array(" rid"=>new MongoId($theObjId )), 
        array(
            "students" => 1,
        )
        );

I want to print it out all the list of the students. I could not manage it by using Foreach loop.

do a json_encode and you will get an array. then you can loop through key / val — Satya
– Satya, Commented Apr 26, 2013 at 11:29
You mean you don't know how to query and return students by class_id? — Adil
– Adil, Commented Apr 26, 2013 at 11:39
@Satya : json_encode do the work. Can we do it without json_encode? — mustafa
– mustafa, Commented Apr 26, 2013 at 11:48

pozs · Accepted Answer · 2013-04-26 11:57:05Z

2

All you need to do is call findOne() instead of find():

$classroom = $collection->findOne(
  array( '_id' => new MongoId($theObjId )), 
  array( 'students' => 1 )
);

$classroom['students']; // will be an array of students

http://php.net/manual/en/mongocollection.findone.php

answered Apr 26, 2013 at 11:57

pozs

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1 Comment

mustafa Over a year ago

Thanks, this also did the job.

Adil · Accepted Answer · 2013-04-26 12:22:07Z

1

$student_list is a MongoCursor of multiple rows. You need to loop through that to get access to the row you're looking for. Like so:

$cursor = $collection->find(array("_id"=>new MongoId($theObjId)), 
        array("students" => 1));

foreach($cursor as $row)
    foreach($row['students'] as $student)
         echo $student["sname"], $student["age"];

Also, consider using findOne. It is better suited to your query.

edited Apr 26, 2013 at 12:22

answered Apr 26, 2013 at 12:13

Adil

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