You can add multiple more checks to see if the data is correct with the rules you set in the statements. cheers!

Check if the number of instructors is too high

if ($data['instructors'] > $maxInstructors) {
    if ($data['participants'] > 0) {
        $errors['instructors'] = "With participants, a maximum of {$maxInstructors} instructors is allowed for {$workshopsReserved} workshop(s).";
    } else {
        $errors['instructors'] = "A maximum of {$maxInstructors} instructors is allowed for {$workshopsReserved} workshop(s).";
    }
}

• If the number of instructors exceeds the allowed limit, an error message is added to the $errors array.

• The message changes slightly depending on whether there are participants.

  Check if the number of participants is too high

if ($data['participants'] > $maxParticipants) {
    $errors['participants'] = "A maximum of {$maxParticipants} participants is allowed for {$workshopsReserved} workshop(s).";
}

• If the number of participants exceeds the allowed limit, an error message is added.
• Check that participants cannot exist without instructors

if ($data['participants'] > 0 && $data['instructors'] == 0) {
    $errors['participants'] = "Participants cannot be registered without instructors.";
}

• Ensures that you cannot have participants in a workshop if no instructors are assigned.

  Return back with errors if any exist

if ($errors) {
    return back()->withErrors($errors)->withInput();
}