PHP Quiz: Who Wants to Be a Millionaire?

WWTBAM.php

<?php
/**
 * WWTBAM: Who Wants to Be a Millionaire?
 *
 * At the end of this file you will find the JSON data structure.
 *
 * Author: Fabian Dennler 
 */

$playing = true;                          // Flag to check if game is running
$index = 0;                               // Index of current question
$storage = "./WWTBAM.json";               // File containing the questionaire
$payout = 0;                              // Contains the actual winning amount
$safepoint = null;                        // Index of last security point

$json = file_get_contents($storage);      // Read JSON file TODO: Check if file exists
$questionaire = json_decode($json, true); // Decode JSON TODO: Check if is valid and not empty

print("\nSo you want to be a millionaire?\n");
printf("Answer the following %d questions ...\n\n", sizeof($questionaire));

while($playing) {
    if(askQuestion($questionaire[$index])) {
        $payout = $questionaire[$index]["WIN"];
        if ($questionaire[$index]["ISSAFE"] == "true") {
            $safepoint = $index;          // Remember this safepoint for fallback
            print("You reached a safepoint ;)\n\n");
        }
        $index++;
    } else {
        $playing = false;
        if (is_numeric($safepoint)) {
            $payout = $questionaire[$safepoint]["WIN"];
            print("You're lucky! Falling into safety net ...\n\n");
        } else {
            $payout = 0;
        }
    }
    // If question index is greater the amount of questions
    if ($index > (sizeof($questionaire) - 1)) {
        $playing = false;
    }
}

if ($payout > 0) {
    printf("Your payout is %d.\n\n", $payout);
} else {
    print("Back to school with empty hands :o\n\n");
}

function askQuestion($question) {
    $delay = 1;                     // Delay between answers and result
    $continue = true;               // Return value
    printf("%s\n", $question["QUESTION"]);
    sleep($delay);
    foreach($question["ANSWERS"] as $key => $answer) {
        printf("%s: %s\n", $key, $answer);
        sleep($delay);
    }
    // TODO: add Lifelines/Jokers
    print("\nEnter your choice: ");
    fscanf(STDIN, "%s", $answer);
    sleep($delay);
    if ($question["RIGHTONE"] === $answer) {
        print("\nCongrats! That's the right answer.\n\n");
    } else {
        print("\nFail! That's the wrong answer.\n\n");
        $continue = false;
    }
    return $continue;
}

// Questionaire as JSON data structure
/*

[
  {
    "QUESTION": "Question 1?",
    "ANSWERS": {
      "A": "A",
      "B": "B",
      "C": "C",
      "D": "D"
    },
    "RIGHTONE": "B",
    "WIN": "100",
    "ISSAFE": true
  },
  {
    "QUESTION": "Question 2?",
    "ANSWERS": {
      "A": "A",
      "B": "B",
      "C": "C",
      "D": "D"
    },
    "RIGHTONE": "C",
    "WIN": "200",
    "ISSAFE": false
  }
]

*/