PHP Help Needed with "Notice: Trying to Access Array Offset on Value of Type Null" Error

[JimmysNetwork]

Hello,

I’m encountering the following error in my PHP game code I am working on currently:

Notice: Trying to access array offset on value of type null in /public_html/rpg/game.php on line 53

Here is the part of my code that seems to be causing the issue:

// Handle POST requests (attacking NPC, etc.)
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $data = json_decode(file_get_contents("php://input"), true);

    if ($data['action'] === 'attack') {
        // Randomly select an NPC from the map
        $npcId = array_rand($npcs);  // Random NPC selection by ID
        if (isset($npcs[$npcId])) {
            $npc = $npcs[$npcId];

I believe it’s related to how I'm trying to access $npcs[$npcId], but I’m not sure why it’s showing as null on line 53. The $npcs array is populated earlier, so I'm not sure why it would be null when I try to access it.

Any help would be greatly appreciated! I believe I am overthinking the solution.

Thanks!

 

[simong1993]

Are you sure its not empty, try dumping it just to make sure
var_dump($npcs);

 

[JimmysNetwork]

Are you sure its not empty, try dumping it just to make sure
var_dump($npcs);

When using var_dump($npcs);

It will dump the data;

array(
    2 => array(
        0 => array(
            "id" => 1,
            "name" => "Goblin",
            "health" => 30,
            "attack" => 5
        ),
        1 => array(
            "id" => 2,
            "name" => "Orc",
            "health" => 50,
            "attack" => 10
        )
    )
)

 

[simong1993]

Did you print out the log $npcs before you call array_rand($npcs)

 

[JimmysNetwork]

Did you print out the log $npcs before you call array_rand($npcs)

Yeah here is my game.php code to make it easier;

<?php
ini_set('display_errors', 1);
error_reporting(E_ALL);

session_start();
require_once 'includes/database.php';
require_once 'includes/functions.php';

// Load data from JSON files
$maps = loadJsonData('data/maps.json');
$npcs = loadJsonData('data/npcs.json');
$items = loadJsonData('data/items.json');
$drops = loadJsonData('data/drops.json');

var_dump($npcs);

// Check if the data was loaded correctly
if (!$maps || !is_array($maps)) {
    echo json_encode(["error" => "Maps data is not valid or empty"]);
    exit;
}
if (!$npcs || !is_array($npcs)) {
    echo json_encode(["error" => "NPCs data is not valid or empty"]);
    exit;
}
if (!$items || !is_array($items)) {
    echo json_encode(["error" => "Items data is not valid or empty"]);
    exit;
}
if (!$drops || !is_array($drops)) {
    echo json_encode(["error" => "Drops data is not valid or empty"]);
    exit;
}

// Check if the user is logged in and fetch their data
if (isset($_SESSION['user_id'])) {
    $userId = $_SESSION['user_id'];
    $user = getPlayerStatistics($userId);  // Fetch the player's stats

    // Ensure the user data is valid
    if (!$user) {
        echo json_encode(["error" => "User data not found"]);
        exit;
    }
} else {
    echo json_encode(["error" => "User not logged in"]);
    exit;
}


// Handle POST requests (attacking NPC, etc.)
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $data = json_decode(file_get_contents("php://input"), true);

    if ($data['action'] === 'attack') {
        // Randomly select an NPC from the map
        $npcId = array_rand($npcs);  // Random NPC selection by ID
        if (isset($npcs[$npcId])) {
            $npc = $npcs[$npcId];

            if ($npc) {
                // Battle logic: NPC attacks player, player attacks NPC
                $playerAttack = rand(5, 15); // Random attack range for player
                $npcAttack = $npc['attack'];

                // Deal damage to the NPC and the player
                $npc['health'] -= $playerAttack;
                $user['health'] -= $npcAttack;

                // Determine the result of the attack
                $playerWins = $npc['health'] <= 0;

                // Experience gain logic
                if ($playerWins) {
                    $user['experience'] += $npc['experience'];

                    // Check if the player leveled up
                    if ($user['experience'] >= calculateExperienceToNextLevel($user['level'])) {
                        $user['level']++;
                        $user['experience'] = 0; // Reset experience for next level
                    }

                    // Calculate TNL (To Next Level)
                    $experienceToNextLevel = calculateExperienceToNextLevel($user['level']);
                    $user['tnl'] = $experienceToNextLevel - $user['experience'];
                }

                // Save updated user data to the database
                saveUserData($userId, $user['health'], $user['level'], $user['experience'], $user['tnl']);

                // Prepare the action log
                $actionLog = [
                    'success' => $playerWins,
                    'playerHealth' => $user['health'],
                    'playerLevel' => $user['level'],
                    'playerExperience' => $user['experience'],
                    'playerTnl' => $user['tnl'],
                    'npcName' => $npc['name'],
                    'npcHealth' => $npc['health'],
                    'experienceGained' => $npc['experience'],
                    'npcAttack' => $npcAttack,
                    'playerAttack' => $playerAttack
                ];

                // Return response with updated stats and action log
                echo json_encode($actionLog);
                exit;
            }
        }
    }
}

?>

 

[Tyrsson]

Update the condition to

if (!empty($npcId) && !empty($npcs[$npcId])) {

By the way, without any var_dumps in the file etc, what code is showing on line 53 in your file because in the file that you posted line 53 is:

$data = json_decode(file_get_contents("php://input"), true);

Edit to add:
What version of php are you running and on what OS?

 

[Tyrsson]

Any movement on this @JimmysNetwork ?