Multiple nested array from MySQL query in PHP - php

Question

I'm using foreach loops to access records in a nested array.
I need to nest 3 arrays (so the first array contains an array, which also contains an array). I'm having success with 2 arrays but I can't get 3 to work.
I had my code working with 2 arrays (which worked just fine) but I can't get 3 arrays to be nested.
This is the result that I want:
[
{
"site_id": "1",
"user_plants": [
{
"user_plant_id": "1",
"site_id": "1",
"plant_id": "1",
"plant_images": [
{
"plant_image_id": "1"
},
{
"plant_image_id": "2"
},
{
"plant_image_id": "3"
},
]
}
]
}
]
My current code:
$query = "SELECT A.site_id FROM sites A WHERE A.user_id='".$user_id."' GROUP BY A.site_id";
$result = $this->conn->query($query);
$json_response = array();
$sites = array();
if ($result-> num_rows > 0) {
while ($item = $result->fetch_object())
$sites[] = $item;
foreach($sites as $item) {
$row_array = (array)$item;
$site_id = $item->site_id;
$user_plants = "SELECT A.user_plant_id, A.site_id, A.plant_id FROM user_plants A RIGHT JOIN sites B ON A.site_id ='".$site_id."'
JOIN plants C ON A.plant_id = C.plant_id GROUP BY A.user_plant_id";
$resultSet = $this->conn->query($user_plants);
$user_plants = array();
if ($resultSet-> num_rows > 0) {
while ($item = $resultSet->fetch_object())
$user_plants[] = $item;
foreach ($user_plants as $item) {
$row_array['user_plants'][] = (array)$item;
$plant_id = $item->plant_id;
$user_plant_id = $item->user_plant_id;
$plant_images = "SELECT A.plant_image_id FROM plants_images A WHERE A.plant_id ='".$plant_id."' UNION SELECT B.plant_image_id FROM user_plant_image B JOIN user_plants C ON B.user_plant_id ='".$user_plant_id."' WHERE C.user_id ='".$user_id."' GROUP BY B.plant_image_id ORDER BY plant_image_id";
$resultSet = $this->conn->query($plant_images);
$plant_images = array();
if ($resultSet->num_rows > 0) {
while ($item = $resultSet->fetch_object())
$plant_images[] = $item;
foreach ($plant_images as $item) {
$row_array['user_plants'][]['plant_images'][] = $item;
}
} else if ($resultSet->num_rows == 0) {
$row_array['plant_images'] = [];
}
}
$json_response[] = $row_array;
}
}
}
return $json_response;
The result of above code:
[
{
"site_id": "1",
"user_plants": [
{
"user_plant_id": "1",
"site_id": "1",
"plant_id": "1"
},
{
"plant_images": [
{
"plant_image_id": "1"
},
{
"plant_image_id": "2"
},
{
"plant_image_id": "3"
},
]
}
]
}
]
How should I adjust the foreach loops above to cater for this?

Answer 1

There's plenty of room for improvement in this code but I've ignored that and tried to keep the code matching yours in this example.
The main changes are:
Create a temporary variable $user_plant_array which we store "plant_images" against
Push that temporary variable to the $site_array at the end of the loop
Rename some loop variables to making it easier to identify what you're referencing
$json_response = array();
$sites = array();
if ($result->num_rows > 0) {
while ($site = $result->fetch_object()) {
$sites[] = $site;
}
foreach ($sites as $site) {
$site_array = (array)$site;
$site_id = $site->site_id;
$user_plants = "SELECT A.user_plant_id, A.site_id, A.plant_id FROM user_plants A RIGHT JOIN sites B ON A.site_id ='" . $site_id . "'
JOIN plants C ON A.plant_id = C.plant_id GROUP BY A.user_plant_id";
$resultSet = $this->conn->query($user_plants);
$user_plants = array();
if ($resultSet->num_rows > 0) {
while ($user_plant = $resultSet->fetch_object())
$user_plants[] = $user_plant;
foreach ($user_plants as $user_plant) {
// create a temporary variable here that we will map
// all "plant_images" to
$user_plant_array = (array)$user_plant;
$plant_id = $user_plant->plant_id;
$user_plant_id = $user_plant->user_plant_id;
$plant_images = "SELECT A.plant_image_id FROM plants_images A WHERE A.plant_id ='" . $plant_id . "' UNION SELECT B.plant_image_id FROM user_plant_image B JOIN user_plants C ON B.user_plant_id ='" . $user_plant_id . "' WHERE C.user_id ='" . $user_id . "' GROUP BY B.plant_image_id ORDER BY plant_image_id";
$resultSet = $this->conn->query($plant_images);
$plant_images = array();
if ($resultSet->num_rows > 0) {
while ($plant_image = $resultSet->fetch_object())
$plant_images[] = $plant_image;
foreach ($plant_images as $plant_image) {
$user_plant_array['plant_images'][] = $plant_image;
}
} else if ($resultSet->num_rows == 0) {
$user_plant_array['plant_images'] = [];
}
// the temporary variable now contains all "plant_images"
// now we can push that to the site array
$site_array['user_plants'][] = $user_plant_array;
}
$json_response[] = $site_array;
}
}
}
return $json_response;

Answer 2

Creating a separate answer as an alternate solution with some code improvements.
"Improvements" being more readability and/or more performant.
A few of the main changes I would suggest as "improvements" have been implemented in this example. The main ones being:
Using prepared SQL statements (not always required but good practice to use, especially in anything accepting user input, also can make for cleaner code)
Reducing the amount of loops (in a few places you were looping just to create an array and then looping again)
Returning/continuing early where possible (helps to prevent unnecessary nesting)
Removing unnecessary if statements (e.g. most of the while loops will be skipped if the results are empty - checking beforehand isn't entirely necessary)
More readable variable names (it's common for new coders to try and abbreviate a lot of variables and often take it too far - making them readable will save you a lot of time when debugging)
The code using mysqli might not be the best as I generally work with PDO.
function getSitesData() {
// assumes that $user_id is set somewhere before this
// assumes that $this->conn references a valid database connection
$sql = "SELECT A.site_id FROM sites A WHERE A.user_id = ? GROUP BY A.site_id";
$query = $this->conn->prepare($sql);
$query->bind_param("i", $user_id);
$query->execute();
$site_result = $query->get_result();
$sites = [];
while ($site = $site_result->fetch_assoc()) {
// using fetch_assoc gives us an associative array
// initialise empty array
$site["user_plants"] = [];
// get user_plants
$sql = "SELECT A.user_plant_id, A.site_id, A.plant_id FROM user_plants A RIGHT JOIN sites B ON A.site_id = ?
JOIN plants C ON A.plant_id = C.plant_id GROUP BY A.user_plant_id";
$query = $this->conn->prepare($sql);
$query->bind_param("i", $site["site_id"]);
$query->execute();
$user_plant_result = $query->get_result();
while ($user_plant = $user_plant_result->fetch_assoc()) {
// intialise empty array
$user_plant["plant_images"] = [];
// get plant images
$sql = "SELECT A.plant_image_id FROM plants_images A WHERE A.plant_id = ? UNION SELECT B.plant_image_id FROM user_plant_image B JOIN user_plants C ON B.user_plant_id = ? WHERE C.user_id = ? GROUP BY B.plant_image_id ORDER BY plant_image_id";
$query = $this->conn->prepare($sql);
$query->bind_param("iii", $user_plant["plant_id"], $user_plant["user_plant_id"], $user_id);
$query->execute();
$plant_image_result = $query->get_result();
while ($plant_image = $plant_image_result->fetch_assoc()) {
$user_plant["plant_images"][] = $plant_image;
}
$sites["user_plants"][] = $user_plant;
}
$sites[] = $site;
}
return $sites;
}