PHP Case Studies & Practical Application 3

Question 1

You inherit a PHP app with no error logging. Users report intermittent blank pages. What is the fastest first diagnostic step?

Accepted Answer

Set error_reporting(E_ALL) and log_errors=On in php.ini, then reproduce the issue

Answer

Enabling full error reporting and logging captures the actual fatal error or exception causing the blank page without exposing it to users.

Question 2

A PHP e-commerce checkout must charge a credit card and then save the order. If the charge succeeds but DB insert fails, what pattern prevents charging without saving?

Accepted Answer

Wrap both operations in a database transaction and rollback if either fails

Answer

A database transaction ensures atomicity: if the DB insert fails after a successful charge, the transaction rolls back and compensating logic can refund the charge.

Question 3

Your PHP application caches rendered HTML in files. After a content update the old cache is served. What is the cleanest cache-busting approach?

Accepted Answer

Delete or overwrite the cached file when content is updated, or use a hash-based cache key

Answer

Invalidating the cache file on content update or keying it by a content hash ensures fresh content is served immediately after changes.

Question 4

A PHP CLI script runs nightly to import 500,000 rows from an external API into MySQL. Memory runs out mid-import. What is the best fix?

Accepted Answer

Use PDO with unbuffered queries and insert rows in batches rather than collecting all data in memory

Answer

Batched inserts with unbuffered streaming keeps memory usage constant regardless of total row count.

Question 5

You need to implement role-based access control in a PHP MVC app. Where is the correct place to enforce authorization checks?

Accepted Answer

In a middleware or base controller that runs before the action method

Answer

Middleware or base controller hooks intercept every request before business logic runs, preventing unauthorized code paths from executing at all.

PHP - PHP Programming Language Practice Test

PHP - PHP Programming Language Practice Test

PHP Case Studies & Practical Application 3