DALT.PHP - Learn Backend by Debugging

Difficulty: Easy — 2 missing directives

What This Challenge Is

The Docker stack has Nginx as the web server and PHP-FPM handling PHP execution. Nginx receives HTTP requests and needs to forward .php files to PHP-FPM — but the configuration is missing the two directives that make this happen.

Without these, Nginx serves .php files as plain text (or returns a 502 Bad Gateway error), and DALT.PHP never runs.

Run the challenge to load the broken config into your project:

php artisan challenge:start docker-broken-nginx

Then open nginx/default.conf in your editor and add the two missing directives inside the location ~ \.php$ block.

Background: How Nginx and PHP-FPM Work Together

Nginx does not run PHP. It's a web server that handles HTTP. When a request arrives for a .php file, Nginx uses the FastCGI protocol to hand it off to PHP-FPM, which does run PHP.

Browser
  │  HTTP request: GET /index.php
  ▼
Nginx (nginx:alpine container, port 80)
  │  FastCGI: "here's a PHP file to run"
  ▼
PHP-FPM (app container, port 9000)
  │  Runs the PHP code
  ▼
Response back through Nginx to browser

The location ~ \.php$ block in the Nginx config is where you configure this handoff.

The Two Missing Directives

1. `fastcgi_pass`

Tells Nginx where to send PHP requests. In Docker Compose, containers talk to each other using service names as hostnames.

Your docker-compose.yml will have a service named app (the PHP-FPM container). PHP-FPM listens on port 9000 by default.

The directive:

fastcgi_pass app:9000;

2. `fastcgi_param SCRIPT_FILENAME`

Tells PHP-FPM the full filesystem path of the PHP file to execute. Without this, PHP-FPM doesn't know which file to run.

The document root inside the app container is /var/www/html/public (matching the WORKDIR + public/ subdirectory). The $fastcgi_script_name variable is Nginx's built-in variable for the script path.

The directive:

fastcgi_param SCRIPT_FILENAME /var/www/html/public$fastcgi_script_name;

Files Involved

nginx/default.conf — the only file you need to edit

Both directives go inside the location ~ \.php$ { ... } block, after include fastcgi_params;.

Verify Your Solution

php artisan challenge:verify

The verifier checks:

fastcgi_pass app:9000; is present
SCRIPT_FILENAME is set
No # TODO comments remain

Testing With the Full Stack

After verifying, you can test the full stack once you have a docker-compose.yml (covered in Lesson 08). For now, confirming the verifier passes is the goal.

Common Mistakes

Wrong service name in fastcgi_pass: If your PHP-FPM container is named differently in docker-compose.yml, the hostname must match. The convention is app.

Missing semicolons: Nginx configs require a semicolon at the end of every directive. Forgetting one causes the entire Nginx config to fail to load.

$document_root$fastcgi_script_name pattern: Some tutorials use fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name. This works if root is set correctly, but the explicit path /var/www/html/public$fastcgi_script_name is more reliable inside Docker where paths must be unambiguous.

What Happens If You Get It Wrong

No fastcgi_pass: Nginx doesn't know where to send PHP requests. You'll see a 502 Bad Gateway error.

No SCRIPT_FILENAME: PHP-FPM receives the request but can't find the file. You'll see a blank page or a PHP error about the script not being found.

Next Steps

After completing both Phase 1 challenges:

Lesson 08: Docker Compose — tie all three containers together into one command: docker compose up

Broken Nginx Config