In use case diagrams, what does an "actor" represent?

Which symbol represents inheritance in UML class diagrams?

What does a filled diamond represent in class diagrams?

What are the four main principles of OOP?

Explain encapsulation with a concrete example.

What is the difference between composition and aggregation?

Explain the Open/Closed principle.

What is the difference between self:: and static:: in PHP?

What are PHP traits and when would you use them?

How can you prevent a class from being inherited in PHP?

What is the purpose of the magic method __toString()?

Which feature of PHP 8 allows type declarations for class properties?

What does PDO mean and why is it preferred over mysql_* functions?

How do prepared statements prevent SQL injections?

Write a PDO connection with proper error handling.

How to manage transactions with PDO?

What is the difference between INNER JOIN and LEFT JOIN?

What are database indexes and when should you create them?

What is the difference between COUNT(*) and COUNT(column)?

What is the difference between git fetch and git pull?

How to undo the last commit without losing the changes?

Explain the difference between git merge and git rebase.

What is the purpose of the .gitignore file?