You seem to be going about everything right..but if you are going to be using the start/end/rate values directly, you shouldn't need the second foreach loop. Something like this should get you going:

$values = array();
foreach($this->taxBand as band) {
    $calculation = ($band['end'] - $band['start']) / $band['rate'];

    $values[calculation;
}
return $values;

I'm doubting this is the work you plan to do, but the point is you can access the inner associative array $band directly.

If you were to use a sub-loop for whatever reason, you could do something like this:

foreach($this->taxBand as band) {
    // Set variables for this band

    foreach($band as $subKey => $value) {
        switch($subKey) {
             case 'start': // do something
                 break;
             case 'end': // do something
                 break;
             case 'rate': // do something
                 break;
        }
    }

    // Calculations finished
}

Nest two foreach loops:

foreach ($array as values) {
    print "$i {\n";
    foreach ($values as value) {
        print "    value\n";
    }
    print "}\n";
}

Here is one way to solve the problem. This function checks each key for a match, then checks the values, recursing if the value is an array. For each test, if the category is found true is immediately returned up the levels of the recursion. Only if no match is found is false returned. Note we use an === comparison with the key so that a category string such as A does not get treated as equal to a key of 0.

function categoryExist(category) : bool
{
    $ce = false;
    foreach (key => $value) {
        if ($category === $key) return true;
        if (is_array($value)) {
            if (categoryExist($value, $category)) return true;
        }
        else {
            if ($category === $value) return true;
        }
    }
    return false;
}

Sample testing code:

$arr = [ 'A', 'B', 'C', 'D' => [ 'E', 'F' => [ 'G', 'H' ] ], 'I' => [ 'J', 'K' ], 'L' ];
foreach (range('A', 'M') as $cat)
    echo "Category '$cat' " . (categoryExist(cat) ? '' : 'not ') . "found\n";

Output:

Category 'A' found
Category 'B' found
Category 'C' found
Category 'D' found
Category 'E' found
Category 'F' found
Category 'G' found
Category 'H' found
Category 'I' found
Category 'J' found
Category 'K' found
Category 'L' found
Category 'M' not found

Demo on 3v4l.org

This is very simple.

Example:

foreach($spellen as $gameName => $value) {
  echo $gameName . "can be played with " . $value['Amount of players'] . " Players, the minimal age is " . $value['Age'] . "and the game has a price of " . $value['price'];
}

With foreach you loop through an array. The $gameName is the key, in your case "Game 1", and so on. The value is an array wicht contains all the values. You get them by $value['valuename'];

Your first foreach() is iterating through the top level of the array, and then your second foreach() is iterating through the second level. Each second level contains "group" and "access".

You only need a single loop;

Also since you're using a function the scope of any changes will be limited to the function, so you should return $grouparray from the function to then check it for changes.

function groupSearch($ldapconn, $user, $innergrouparray) {
    foreach ($innergrouparray as $key => $value) {
        $innergrouparray[$key]['access'] = checkGroupMembership($ldap, $user, $value['group']); // this returns true or false
    }

return $innergrouparray;
}

$newgrouparray = groupSearch($ldap, $user, $grouparray);
print_r($newgrouparray);

This should do it... (check the privilege level)

foreach($array as $level => $priv){
    // check for privilege level
    if($level >= $accessLevel){
        // loop through privilege array
        foreach($priv as $command => $list){
            foreach($list as $trigger => $description)

            }
        }
    }
}

On a side note, instead of using string keys for level you could use array indicies, and that would allow the combined outer foreach/if combination to be written as

for($i = $accessLevel; $i >= 0; $i--){
   $priv = $array[$i];
   //...
}