Learn Functional Programming in PHP/

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Challenge 1: Eliminate Exceptions Using the Either Monad

Challenge 1: Eliminate Exceptions Using the Either Monad

Test your knowledge by rewriting the given code without using any exceptions.

We'll cover the following...

A code snippet is given below. It has an authenticateUser function that authenticates the provided username and password with the stored username and password. If authentication fails, the program throws an exception.

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<?php
const USER_DATA = [
  'password' => '$2y$10$gaGFDPMaVRS61ONjnkGQAODo64voLOUJK1AlokiZY2HY3QiPE4zHq',
  'username' => 'kelly92',
  'admin' => false,
]; // valid password is trap_223
function authenticateUser(string $username, string $password): array
{
  if ($username !== USER_DATA['username']) {
    throw new Exception('Sorry, your username is invalid');
  }
  if (!password_verify($password, USER_DATA['password'])) {
    throw new Exception('Sorry, your password is invalid');
  }
  return USER_DATA;
}
 
authenticateUser('Some_User_Name','Some_Password');
?>

Problem statement

Eliminate the exception in the snippet above by rewriting the authenticateUser as a two-track Either monad-based function. You have to perform the following tasks to complete the challenge:

  1. If the provided username is not valid, then the string returned by the function ...