Getting all ancestors of an element from a table - php

Question

I am building a badges app in CodeIgniter using a MySQL database. There are 3 types of badges: level 1, level 2 and level 3 badges.
Each level 2 badge is awarded once you get all the required level 1 badges and each level 3 badge is awarded once you get all the required level 1 and level 2 badges. There is also a level 3 badge that requires getting 4 level 3 badges.
I have the following database table for my badges relations:
badge_id - children_id
1 - 20
1 - 25
20 - 40
20 - 45
26 - 40
25 - 39
40 - 50
I need a function that returns me all the ancestors of a badge.
For example, if the function recieved the argument 50 it would return: 40, 26, 20, 1. Any ideas?

Answer 1

If you want to handle it by pure mysql, you need to declare a mysql stored procedure which has some depth limitations.
Instead of that I would recommend using a simple recursive PHP function to return what you need:
function get_ancestors($child_id, $badges)
{
$found = array();
foreach($badges as $k => $row){
if ($row['children_id'] == $child_id){
$found = array_merge($found, get_ancestors($row['badge_id'], $badges));
$found[] = $row['badge_id'];
}
}
return $found;
}
The $badges variable holds all the rows from your badges relations table, just simply read it out from the database.
Based on the example you gave, for the following call
get_ancestors(50, $badges);
the output would be:
Array
(
[0] => 1
[1] => 20
[2] => 26
[3] => 40
)