Creating nested json for hotel system - php

Question

I want to create a nested json that comes with post.
I have 3 fields. Adults, children and baby. But, there are also dates for children and baby areas. For example; Children 1 Birthday, Children 2 Birthday, Baby 1 Birthday, Baby 2 Birthday
When I try with the code below, I can't print child dates by room. Writes in bulk. How can I POST with php like json below?
+---------+----------+-------+
| Adults | Children | Baby | (select box field)
+--------------------+--------
| 1 | 0 | 0 |
+--------------------+--------
| 2 | 1 | 1 | (also available for children and baby areas)
+--------------------+-------+
| 3 | 2 | 2 |
+---------+----------+-------+
rooms: [
{
adults: 2,
child: [
child_total: 1
child_date: [
"2017-08-10"
],
],
baby: [
baby_total: 1
baby_date: [
"2017-07-01"
],
],
},
{
adults: 1,
child: [
child_total: 2
child_date: [
"2017-08-08",
"2017-08-09"
],
],
baby: [
baby_total: 2
baby_date: [
"2017-06-08",
"2017-05-09"
],
],
}
],
foreach ($this->input->post('adults') as $key => $value) {
foreach ($_POST['child_total'] as $value2) {
$child_date = [];
foreach ($_POST['child_date'] as $key2 => $value3) {
$child_date[] = $value3;
}
}
$rooms[] = array(
'adults' => $_POST['adults'][$key],
'child' => array(
'child_total' => $_POST['child_total'][$key],
'child_date' => $child_date
)
);
}
print json_encode($rooms, JSON_PRETTY_PRINT);