Debugging With AI

1. THE CODE:
   Paste the function/section where the error is (not the entire 500-line file)

2. THE ERROR:
   Exact error message, including file name and line number

3. WHAT I DID:
   Exact steps to reproduce ("I submitted the form with email='test@test.com'")

4. WHAT I EXPECTED:
   What should have happened ("it should redirect to /dashboard")

Template:
"Here is my code: [paste code]
Error: [exact error message with line number]
I trigger this by: [steps to reproduce]
Expected behavior: [what should happen]
Fix it."

> My PHP code throws this error when I try to login:
  Fatal error: Uncaught PDOException: SQLSTATE[42S22]:
  Column not found: 1054 Unknown column 'email_address' in 'where clause'
  in /app/models/UserModel.php:47

  Here is the login function:
  [paste UserModel::login() method]

  Fix the query to use the correct column name.

> My login form submits with no error, but the user is not logged in.
  The page just reloads. Here is the login() method:
  [paste the method]

  When I submit: email=test@example.com, password=Test1234!
  Expected: redirect to /dashboard and session $_SESSION['user_id'] set
  Actual: page reloads, session not set

  Find the bug and fix it.

> My JavaScript throws this error in the browser console:
  TypeError: Cannot read properties of null (reading 'addEventListener')
  at initForm (app.js:23:35)

  Here is the relevant code:
  [paste initForm function]

  This happens when I open the page. Fix it.

> This PHPUnit test is failing:

  Test: UserTest::testCreateWithDuplicateEmail
  Failure: Expected exception NotUniqueException to be thrown but it was not.

  Here is the test:
  [paste test method]

  Here is the create() method it tests:
  [paste UserModel::create()]

  The test expects an exception when inserting a duplicate email.
  Fix the create() method to throw NotUniqueException when email already exists.

# Error messages:
"I get this error: [error]. Here is the relevant code: [code]. Fix it."
"PHP Warning: [message]. Which line causes it and how do I fix it?"
"Uncaught exception: [message] at [file:line]. Here is that code: [code]."

# Wrong output:
"This function returns [wrong value] but should return [correct value]. Here is the code: [code]."
"This SQL query returns 0 rows but there is data in the table. Query: [sql]. Fix it."
"The page shows a blank white screen. Error logs show: [log line]. Here is index.php: [code]."

# Behavior bugs:
"Form submits but nothing is saved to the database. Handler: [code]. Database table: [schema]."
"Login works but session expires immediately. Here is my session handling: [code]."
"The file upload works on localhost but fails on the live server. Error: [message]. Code: [code]."

# Database bugs:
"This query is very slow (takes 10 seconds). Explain why and add indexes if needed. Query: [sql]. Table has 500,000 rows."
"My JOIN is returning duplicate rows. Query: [sql]. Expected one row per user."

# CSS/HTML bugs:
"My Bootstrap card layout breaks on mobile screens. HTML: [code]. CSS: [code]. Fix it."
"The sticky navbar overlaps my page content. CSS: [code]."

# API/network bugs:
"My API call returns 200 but the response body is empty. PHP endpoint: [code]. JS fetch: [code]."
"CORS error: Access-Control-Allow-Origin header missing. My PHP endpoint: [code]. Fix headers."

# After applying the fix and still getting an error:
"I applied the fix but now I get a different error:
 [new error message]
 The code now looks like: [updated code]"

# If the behavior is still wrong:
"The error is gone but the behavior is still wrong.
 I am getting [what I see] instead of [what I expect].
 Here is the updated code:"

# To add a debug trace:
"Add var_dump() / console.log() statements to help me trace
 what value each variable has at each step."

# To isolate the problem:
"Create a minimal test script that reproduces this bug in isolation
 (no framework dependencies)."

# Nuclear option - start fresh:
"Forget the previous attempts. Here is the original requirement:
 [describe what you need from scratch]. Write it again correctly."

"I have a bug I cannot track down. Here is all the context:

Environment: PHP 8.2, MySQL 8, Apache on Ubuntu 22.04
The bug: Users report that sometimes their cart is empty after checkout
  - Happens about 10% of the time
  - Cannot reproduce locally
  - Only happens on the live server
  - Server is under high load when it happens

Relevant code:
[paste cart.php checkout section]

Database tables involved:
[paste CREATE TABLE for carts and orders]

What I have tried already:
- Added session_write_close() before redirect
- Checked that DB transactions are committed

What is the most likely cause and how do I add logging to confirm?"