Question

I’ve set up a database table like so:

table: group
id     name          subGroupOf
1      grandparent   NULL
2      parent           1
3      child            2

Here’s what I’m trying to do in php:

When a user accesses a page, the page tells the auth() function they require ‘child’ permissions. Because ‘child’ is a subgroup of ‘parent’, members of both groups should get permission. But, parent is a subgroup of ‘grandparent’, so members of all three groups should have access.

Since there is no limit to how many subgroups could be nested, I knew I would need a loop. But I’m totally drawing a blank.

I know it needs to check if the group is a subGroupOf, and if so, validate the parent group. Here’s what I have so far:

        // Get group of current user
        $group = mysqli_query($cxn,'SELECT group FROM user WHERE id='.$userID);

        // Compare group to permissions
        if($group == $permissions)
            return TRUE;

        // Check if group is a sub group
        $subGroupOf = mysqli_query($cxn,'SELECT subGroupOf FROM group WHERE id="'.$group.'"');
        if($subGroupOf == NULL)
        {
            // Wrong permissions
        }

        // Check if the parent group matches permissions
        if($subGroupOf == $permissions)
            return TRUE;

Somehow I need to loop that last part, and stop when it gets to

$subGroupOf == NULL

I’m fairly new to programming, so I’m still figuring out the logic…Any ideas? I don’t need the whole thing written for me (that code is summarized anyways), I just need help figuring out the structure..

Answer 1

Another method, but you still need a function for recursion:

1. Create a function that adds the group’s hierarchy to an array
2. Loop through the array of groups, and check against your permissions.

The function

function getGroupHierarchy($groupId, $cxn)
{
    $groupArray = array();

    //Push the group to the array..
    $groupArray[] = $groupId;

    //Get the parent id of this group
    $subGroupOf = mysqli_query($cxn,'SELECT subGroupOf FROM group WHERE id="'.$groupId.'"');

    //There is no parent, just return the array.
    if($subGroupOf == NULL)
    {
        return $groupArray;
    }

    //Continue checking the parent group(s).
    getGroupHierarchy($subGroupOf, $cxn);
}

Calling the function, and checking against permissions:

// Get group of current user
$groupId = mysqli_query($cxn,'SELECT group FROM user WHERE id='.$userID);

$allGroups = getGroupHierarchy($groupId, $cxn);

//Compare each group to permissions.
foreach($groupArray as $group)
{
    if($group == $permissions)
        return TRUE;
}