What are the key differences between PHP 5 and PHP 7, and how do they affect performance and features?

How do you handle errors and exceptions in PHP, and what best practices should be followed?

What is the purpose of Composer in PHP, and how does it improve dependency management?

How can you secure a PHP application against common vulnerabilities like SQL injection and cross-site scripting (XSS)?

What are the differences between include, require, include_once, and require_once in PHP?

How do sessions work in PHP, and what are the best practices for managing user sessions?

What is the role of PDO (PHP Data Objects) in database interaction, and how does it differ from using the MySQLi extension?

How can you implement RESTful APIs using PHP, and what tools or frameworks can facilitate this process?

What are traits in PHP, and how do they differ from traditional inheritance?

How do you optimize the performance of a PHP application, and what tools can assist in profiling and debugging?