PHP/MYSQL - Counting and comparing entries in a myqsl table with php - php

Question

I was wondering if anybody can help me out/point me in the right direction.
I have a database with a table that includes incremental id, name, unique id, and the parent uuid of fictional characters.
The table shows the following people...
John (Parent not listed)
Steve (Parent listed as John)
Mark (Parent listed as John)
Kevin (Parent listed as Steve)
Adam (Parent listed as Mark)
**ID, NAME, UUID, PARENT_UUID**
1, John, 0001, none
2, Steve, 0002, 0001
3, Mark, 0003, 0001
4, Kevin, 0004, 0002
5, Adam, 0005, 0003
So in this example, John has 2 sons, Steve and Mark... each of whome have a son, Kevin and Adam.
What I want to do, is (on an already made profile page) show the number of family members.
So going to Johns page, I would see "John (4 Descendents)", and if I went to Marks page, I'd see "Mark (1 Descendents)"
Allowing me to list how many family members, in lower generations are found in the table.
I am able to print a list of all family members... using:
$sql = "SELECT * FROM users";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
echo $row["uuid"]. "<br>";
}
}
But now I want to find out for each $row['uuid'] how many descendents each entry has.
I tried doing something like the following:
$sql = "SELECT * FROM users";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
$sql = "SELECT * FROM users WHERE parent_uuid = '".$row['uuid']."'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
$numOfDescendents = $result->num_rows;
}
}
}
But then I realised that not only does this not work (it grabs the number of the first row and stops), that using this logic, if I have a family with 20+ generations, I'm going to need to have 20+ while loops nested within each other, checking each generation.
So I'm wondering, is this even possible?
There's probably an easy way, but after 3/4 days of headaches and frustration I'm finally asking for help =)
My end goal is to have a php file that checks through the table for all users, and totals their descendents by counting how many people in the table use their uuid as a parent_uuid... as in the example at the start... John would have 4, Mark would have 1, Steve would have 1, Kevin would have 0, and Adam would have 0.
Thanks in advance for any guidance =)

Answer 1

You can use a recursive function to solve this. Note - I am passing the entire input to the recursive array which I do not recommend. If you are using a class set the input as a property of the class or you can use global which is also not recommended.
$input = [
['id' => 1, 'name' => 'John', 'UUID' => 0001, 'PARENT_UUID' => null],
['id' => 2, 'name' => 'Steve', 'UUID' => 0002, 'PARENT_UUID' => 0001],
['id' => 3, 'name' => 'Mark', 'UUID' => 0003, 'PARENT_UUID' => 0001],
['id' => 4, 'name' => 'Kevin', 'UUID' => 0004, 'PARENT_UUID' => 0002],
['id' => 5, 'name' => 'Adam', 'UUID' => 0005, 'PARENT_UUID' => 0003],
];
function getDescendents($uuid, $input, $count = 0, $descendants = [])
{
foreach ($input as $user) {
if ($user['PARENT_UUID'] === $uuid) {
$count++;
$descendants[] = $user['UUID'];
}
}
if (!empty($descendants)) {
$new_uuid = array_shift($descendants);
return getDescendents($new_uuid, $input, $count, $descendants);
}
return $count;
}
$result = [];
foreach ($input as $user) {
$result[$user['name']] = getDescendents($user['UUID'], $input);
}
echo(json_encode($result));
Output -
{"John":4,"Steve":1,"Mark":1,"Kevin":0,"Adam":0}
The key in the above object is the user's name and the value is the number of descendants.