PHP PDO output to specific Json Format

I have been trying to get a query output formatted in a specific way but I am surely doing something wrong. Could anyone that knows what I am doing wrong give me a hand? Thanks a lot.

I have the following db call:

     $sql = "SELECT tbl1.spec_num As spec_num,
                    IF(tbl1.spec_fld, 'TRUE', 'FALSE') As spec_fld,
                    tbl2.auth_id As auth_id
            FROM spec_table tbl1
                JOIN spec_auth tbl2 ON tbl1.id=tbl2.spec_table_id
            WHERE tbl1.spec_fld=1
            AND tbl2.enb=1;";
                      

If I run this query in the db (mysql) I get this:

spec_num                                spec_fld    auth_id
123413253242135234213432112345DDDDDDDG  TRUE        1234567
123413253242135234213432112345DDDDDDDG  TRUE        3423435
123413253242135234213432112345DDDDDDDG  TRUE        9234245

When I make a call to the DB in PHP using PDO I do the following:

    $stmt = $connection->prepare($sql); 
    $stmt->execute();
    while ($result = $stmt->fetch(PDO::FETCH_ASSOC)) {
        $result_json = json_encode($result);
        echo $result_json;
    } 

My echo inside the loop shows this:

{"spec_num":"123413253242135234213432112345DDDDDDDG","spec_fld":"TRUE","auth_id":"3423435"}
{"spec_num":"123413253242135234213432112345DDDDDDDG","spec_fld":"TRUE","auth_id":"9234245"}

But what I need now is to create a variable ($dtp) outside the while loop that looks like this:

$dtp = [    
   'spec_num' => '123413253242135234213432112345DDDDDDDG',
   'spec_fld' => TRUE,  
   'auth_ids' => [          
      '1234567',        
      '3423435', 
      '9234245',        
      ],    
   ];

Any ideas on the best way to do this? Thanks again in advance.

Answer

Just use

$arr = $stmt->fetchAll(PDO::FETCH_ASSOC);

and you get an array like

$arr = [
["spec_num" => "123413253242135234213432112345DDDDDDDG","spec_fld" => TRUE,"auth_id" => "1234567"],
["spec_num" => "123413253242135234213432112345DDDDDDDG","spec_fld" => TRUE,"auth_id" => "3423435"],
["spec_num" => "123413253242135234213432112345DDDDDDDG","spec_fld" => TRUE,"auth_id" => "9234245"],
];

You want to create such an array:

$dtp = [    
   'spec_num' => '123413253242135234213432112345DDDDDDDG',
   'spec_fld' => TRUE,  
   'auth_ids' => [          
      '1234567',        
      '3423435', 
      '9234245',        
      ],    
   ];

It only makes sense to create this structure it if the SQL query ensures that spec_num and spec_fld are identical in all lines.

The solution for this special case is very simple:

$dtp = [
  "spec_num" => $arr[0]["spec_num"],
  "spec_fld" => $arr[0]["spec_fld"],
  "auth_id" => []
];
foreach($arr as $key => $row){
  $dtp["auth_id"][] = $row["auth_id"];
}

If spec_num and spec_fld are not identical in all lines, you must first group by spec_num and then by spec_fld. The solution is then a 4 dimensional array.