PHP Case Studies & Practical Application 4

Question 1

A PHP application uses include() to load template files based on a URL parameter like ?page=about. What vulnerability does this create?

Accepted Answer

Local File Inclusion (LFI), allowing attackers to read arbitrary server files

Answer

Using unvalidated user input in include() lets attackers traverse the filesystem and read sensitive files like /etc/passwd.

Question 2

You are profiling a PHP application and find that a database query runs 200 times per page load for the same data. What is the best solution?

Accepted Answer

Cache the query result in memory (APCu or Redis) for the duration of the request or longer

Answer

Caching repeated identical queries eliminates redundant database round-trips, the root cause of the N+1 or repeated-fetch problem.

Question 3

A PHP form saves a user bio with HTML tags to a database and later displays it. Which step is critical at display time?

Accepted Answer

Escape output with htmlspecialchars() when rendering the bio in HTML

Answer

Escaping at output time using htmlspecialchars() converts characters like < and > into safe HTML entities, preventing XSS.

Question 4

Your PHP application generates PDF invoices using a library and temporarily writes them to /tmp. What risk exists if multiple users generate invoices simultaneously?

Accepted Answer

Race conditions where one user's file overwrites another's if filenames are not unique

Answer

Using predictable or shared filenames in a temp directory under concurrent load causes file collisions; use tempnam() or a UUID-based name per request.

Question 5

A PHP application must queue background jobs (e.g., sending emails) without blocking the HTTP response. What is the correct approach?

Accepted Answer

Push jobs to a message queue like RabbitMQ or Redis List and process them with a worker script

Answer

A message queue decouples job creation from execution, allowing the HTTP response to return immediately while workers process jobs asynchronously.

PHP - PHP Programming Language Practice Test

PHP - PHP Programming Language Practice Test

PHP Case Studies & Practical Application 4