Moodle how to find out the role of the logged in user

moodle, php

Solution

checking user is an admin or not

$admins = get_admins();
$isadmin = false;
foreach($admins as $admin) {
    if ($USER->id == $admin->id) {
        $isadmin = true;
        break;
    }
}

use the result for functions

if ($isadmin) {
    echo "you are an admin";    
} else { 
    echo "you are not an amidn";
}

Problem

How to get context/role of logged in user in moodle? I am trying to implement a context-aware block. The block would suggest the right quizzes to its users based on their moods. Role can be a teacher, student, teacher assistant or admin. I have already found the `get_context_instance()` & `has_compatibility()` functions, but I don't know how to use them for this purpose.

Original source