Fixing HTTP ERROR 500 While Using PHP

When I enter my login credentials and submit them on my site’s web script, I get this error message:

This page isn’t working… [Site URL] is currently unable to handle this request. HTTP ERROR 500.

To troubleshoot, I check the developer tools (DevTools) > Console and see:

crbug/1173575, non-JS module files deprecated.
(index):7288

When I expand line 7288, I see this additional message:

"No resource with given URL found."

However, if I refresh the page, I find that I’m successfully logged in.

Explanation:

The HTTP ERROR 500 is a server-side error, which often occurs due to issues in the server script, server misconfiguration, or code execution errors. Below, I’ll walk through steps to troubleshoot and potentially resolve the issue, including how to check and update code to address the error you’re encountering.

Check the Server Error Logs:

The first step in troubleshooting HTTP ERROR 500 is to check your server’s error logs. This log will provide more specific information about the root cause of the issue.

1. Locate your server logs:
   • For Apache: /var/log/apache2/error.log
   • For Nginx: /var/log/nginx/error.log
   • If using a specific hosting service, look in the hosting dashboard for “Error Logs.”
2. Look for any specific errors that align with the time you attempted to log in. This will help narrow down the exact issue.

Identify Potential Coding Errors:

Given the specific console message, crbug/1173575 indicates deprecated JS files, and No resource with given URL found suggests a missing file or path. This could mean either:

• A JavaScript module or resource your code is trying to load is missing or incorrect.
• The code handling the login process has issues, such as an undefined variable or misconfigured function.

Debug the JavaScript and Server-Side Script

Check your login script for issues. Here’s a basic outline of what the code should look like and where potential fixes might be applied.

Example Code Fix in JavaScript (Frontend)

Verify that any modules, scripts, or resources loaded during login are accessible. Here’s a simple way to ensure resources load correctly.

Check resource URLs: Make sure the URLs for all modules or scripts are correct. Replace placeholders with actual paths

code// Verify resource URLs
const script = document.createElement('script');
script.src = "/path/to/your/module.js"; // Ensure path is correct
document.head.appendChild(script);

// Check for errors during loading
script.onerror = function() {
    console.error("Failed to load the module.");
};

Check and update deprecated code: If you have outdated code, update it to avoid deprecated modules

// Avoid deprecated syntax or update code according to new standards
import { yourFunction } from './path/to/yourFunction.js'; // Use relative or absolute paths

Example PHP or Backend Script Fix

Since refreshing allows the user to log in, there might be an issue with session handling or error handling in the PHP script.

Check session start and error handling: Ensure the PHP script properly initializes sessions and handles errors.

code<?php
session_start(); // Start session for login

try {
    // Assume $db is your database connection
    $username = $_POST['username'];
    $password = $_POST['password'];

    // Query to check credentials
    $stmt = $db->prepare("SELECT * FROM users WHERE username = :username AND password = :password");
    $stmt->bindParam(':username', $username);
    $stmt->bindParam(':password', $password);
    $stmt->execute();

    if ($stmt->rowCount() > 0) {
        $_SESSION['logged_in'] = true;
        header("Location: /dashboard.php"); // Redirect after successful login
    } else {
        throw new Exception("Invalid login credentials.");
    }
} catch (Exception $e) {
    error_log($e->getMessage()); // Log the error
    header("HTTP/1.1 500 Internal Server Error"); // Send HTTP 500 error header
    echo "An error occurred. Please try again later.";
}
?>

Error Handling and Logging: Include error handling and logging to capture and resolve any underlying issues without crashing the server.

Clear Cache and Check Console:

After making adjustments, clear the cache, cookies, and server cache (if applicable). Then, try logging in again to verify if the issue persists.

Use Fallback Code for Missing Modules:

If a module or file fails to load, handle this gracefully with fallback options.

code// Example fallback
if (typeof someFunction === "undefined") {
    console.warn("Module not found. Using fallback.");
    function someFunction() {
        console.log("Fallback function in place of missing module.");
    }
}

Following these steps should help identify and address the root causes of your HTTP ERROR 500. If the problem persists, double-check all URLs, modules, and dependencies to ensure they’re correctly configured and accessible.