find（）查询MongoDB for php

Hi i am using mongoDb for my new project. I am trying to find values from mongodb database. My mongoDB database collection name is: test and json format is below

{
"College": [
    {
        "name": "tamy",
        "roll_no": "1"
    },
    {
        "name": "abhi",
        "roll_no": "2"
    },
    {
        "name": "jack",
        "roll_no": "3"
    }
],
"School": [
    {
        "name": "zack",
        "roll_no": "1"
    },
    {
        "name": "mac",
        "roll_no": "2"
    },
    {
        "name": "john",
        "roll_no": "3"
    }
]
}

**And i want to find the name:abhi from test collection ** and my mongodb find query in php

 $criteria = array( 
                'College'=> array(
                    'name'=> 'abhi'
   ));
$cursor = $collection->find($criteria);

but its not returning any value. if i am displaying in php by using print_r.

print_r(iterator_to_array($cursor));

displaying empty array()

I need output like this: name : jack roll_no : 3

plz help me..

The key "College" is an array, your trying to treat it as a "subdocument" (but that wouldnt allow for multiple colleges to be stored)

You want the elemMatch keyword here I believe: http://docs.mongodb.org/manual/reference/operator/query/elemMatch/

EDIT: After looking at this again, I think you have your structure a little out of whack. How many "students" will there be per college or school? Keep in mind each parent document can not exceed 10mb, and when you select a document, the entire document must be sent back across the connection (unless you are using aggregate or map/reduce. I would think you may want to have a collection of Persons and then a key associating a person to... something else.