PHP PDO output to specific Json Format

Question

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.

Will the spec_num always be the same or do you want to be able to cope with more than one spec_num — RiggsFolly
– RiggsFolly, Commented Nov 15, 2022 at 15:30
The spec_num will always be the same. Sorry I did not see this comment earlier — carol1287
– carol1287, Commented Nov 15, 2022 at 20:46

jspit · Accepted Answer · 2022-11-16 08:01:40Z

1

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.

edited Nov 16, 2022 at 8:01

answered Nov 16, 2022 at 7:42

jspit

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1 Comment

carol1287 Over a year ago

THANK YOU SO MUCH, Your solution is much simpler and actually works. Much appreciate it thanks. One typo here, "auth_id" => [] should be "auth_ids" => [] :)

RiggsFolly · Accepted Answer · 2022-11-15 15:52:45Z

Dont convert things to JSON until you have completed building the array or object

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

You could simplify that to

$stmt = $connection->prepare($sql); 
$stmt->execute();
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC) {
echo json_encode($rows);

PART 2

First sort the resultset in spec_num order

$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
        ORDER BY spec_num";

Then the code changes. Build the dtp array bit by bit, I made this able to cope with more than one spec_num being selected

$stmt = $connection->prepare($sql); 
$stmt->execute();

$last_spec_num  = NULL;
$dtp = [];
$tmp = [];

while ($row= $stmt->fetch(PDO::FETCH_ASSOC)) {

    if ( $last_spec_num !== NULL ) {
        // first time through to create a $tmp
        $tmp = ['spec_num' => $row['spec_num'],
                'spec_fld' => $row['spec_fld'],  
                'auth_ids' => $row['auth_id']
               ];
        $last_spec_num = $row['spec_num'];
    }

    if ( $last_spec_num != $row['spec_num'] ) {
        // got new spec_num
        $dtp[] = $tmp;
        $tmp = [];      // init tmp
        // load this row into the new $tmp
        $tmp = ['spec_num' => $row['spec_num'],
                'spec_fld' => $row['spec_fld'],  
                'auth_ids' => $row['auth_id']
               ];
        // set the new las spec num
        $last_spec_num = $row['spec_num'];
    } else {
        // same spec_num
        $tmp['auth_ids'][] = $row['auth_id'];
    }       
}
// echo json_encode($dtp); here if thats what you want to do

Thanks a lot for your help. This throws an error here: $tmp['auth_ids'][] = $row['auth_id']; Error = Uncaught Error: [] operator not supported for strings Any idea what that could be?

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