How do I create a JSON-encoded 2D array? - php

Question

I'm trying to create a two-dimensional array with the following code, but it gets JSON-encoded as an object. How do I fix this?
$result = $bd->query("select * from contenidos where idfolleto=$idf order by fila");
$arr = array();
if ($result) {
while ($row = mysqli_fetch_object($result)) {
$filaAct = $row->fila;
$arr[$filaAct][] = (array) $row;
}
}
echo json_encode($arr);
The output is:
{
"1": [{
"id": "6",
"idfolleto": "1",
"fila": "1",
"orden": "1",
"tipo": "carrousel",
"titulo": "",
"subtitulo": null,
"color1": null,
"color2": null,
"color_fondo": null
}],
"2": [{
"id": "7",
"idfolleto": "1",
"fila": "2",
"orden": "1",
"tipo": "texto-imagenes",
"titulo": "Texto 1",
"subtitulo": null,
"color1": null,
"color2": null,
"color_fondo": null
}, {
"id": "8",
"idfolleto": "1",
"fila": "2",
"orden": "2",
"tipo": "texto-imagenes",
"titulo": "Texto 2",
"subtitulo": null,
"color1": null,
"color2": null,
"color_fondo": null
}],
"3": [{
"id": "9",
"idfolleto": "1",
"fila": "3",
"orden": "3",
"tipo": "texto-imagenes",
"titulo": "Texto 3",
"subtitulo": null,
"color1": null,
"color2": null,
"color_fondo": null
}]
}

Answer 1

You would have to index it without using your own defined indices.
If you must maintain using fila as the indices then you have to understand that the encoded JSON will be an object. You can json_decode it back into an array though like: json_decode($json, 1);
Otherwise before encoding the array you could call: $arr = array_values($arr); which would result in the array being encoded as a JSON array once you call json_encode.

Answer 2

If you're sure that your fila fields will contain "indexes" (I mean continuous integers starting from 0), then you can convert them to integers using intval.
if ($result) {
while ($row = mysqli_fetch_object($result)) {
$arr[intval($row->fila)][] = (array) $row;
}
}
Otherwise, it probably would be better to just group the records and create an array of the groups.
if ($result) {
$groups = array();
while ($row = mysqli_fetch_object($result)) {
$groups[$row->fila][] = (array) $row;
}
$arr = array_values($groups);
}