Question

In my farming related Android app user sends crop’s name to PHP webservice and that webservice should return details about that crop.

Here’s the sample structure of database.

Crop_Master:Crop_Id , Crop_Name , Seed_Rate , Fertilizer
Pest: Crop_id , Pest_Name

Now I know about fetchAll() function of PDO and convert it to JSON array if the data is coming from a single table.

Like this: Here data comes from Crop_Master table and works fine.

$query1="select seed_rate,fertilizer_dosage from crop_master where crop_id='$crop_id'";

$res=$db->query($query1);

$output=$res->fetchAll(PDO::FETCH_ASSOC);

print(json_encode($output));

But I don’t know how I can create a single “output” array when the data is coming from multiple tables.

Suppose I want to create a JSON array like this:

[
   {
      "seed_rate":"value_from_db"
      "fertilizer":"value_from_db"
      "pests":
              [{"pest_name:"value_from_db"}
               {"pest_name:"value_from_db"}
                .
                .
                .
               ]
    }
]

Then how can I run multiple queries and make a single output array?

Answer 1

You need to add array element “pests” to the array $output and populate it… How, will depend on the database structure, but likely something like

$query1="select seed_rate,fertilizer_dosage from crop_master where crop_id='$crop_id'";    
$res=$db->query($query1);    
$output=$db->fetchAll(PDO::FETCH_ASSOC);

$query2="select pest_name from pests, crop_pests where pests.pest_id = crop_pests.pest_id and crop_pests.crop_id='$crop_id'";    
$res=$db->query($query2);    
$output["pests"]=$db->fetchAll(PDO::FETCH_ASSOC);

print(json_encode($output));

So, point is, you need to have array of pests as element of your $output array. My $query2 is of course just an example and needs to be adjusted for your database