PHP nested array from flat MySQL query result

kabauter Published at Dev

kabauter

I need to create a line chart using highcharts.com js. The plugin requires JSON data with the following structure:

series: [{
    {
    name: 'book 2',
    data: [
            1970, 120,
            2001,  50,
            2005, 180,
            2014,  50
          ]
    }, 
    {
    name: 'another book',
    data: [
            1970, 120,
            2001,  50,
            2005, 180,
            2014,  50
          ]
    }
            }]

(the data is just an example)

I want to query the needed data from a MySQL Database. The data is extracted with the meekrodb.com library in PHP.

$results = DB::query("SELECT booktitle, EditionNr, Year FROM editions");

The query so far outputs this flat array:

    (
        [0] => Array
            (
                [booktitle] => booktitle_a
                [EditionNr] => 11
                [Year] => 2012
            )
        [1] => Array
            (
                [booktitle] => booktitle_a (the same)
                [EditionNr] => 12
                [Year] => 2013
            )

        [2] => Array
            (
                [booktitle] => another_booktitle
                [EditionNr] => 1
                [Year] => 2000
            )
...

The top level indexes correspond to the rows of the result of the query. However the data output must be hierarchial. How can I convert it to a nested array that looks like this?

Array
(
    [name] => book_title_a
    [data] => Array
        (
            [0] => 2012, 11  // these are the rows Year (=2012) and EditionNr (=11th edition)
            [1] => 2013, 12
        )

    [name] => another_book_title
    [data] => Array
        (
            [0] => 2000, 1
            [1] => 2011, 2
            [2] => 2012, 3
        )
)

I appreciate your help.

-Andi

Phil

Try something like this:

$data = array();

foreach ( $rows as $row ) {
  $bookTitle = $row['booktitle'];
  if ( !isset( $data[$bookTitle] ) ) {
    $data[$bookTitle] = array( "name" => $bookTitle, "data" => array() );
  }
  $data[$bookTitle]['data'][] = array( $row['Year'], $row['EditionNr'] );
}

echo json_encode( array_values( $data ) );

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