1. Differentiating echo and print
This is a classic question that highlights the subtle performance difference and return values of the two common output statements.
2. What is the difference between == and === operators?
This question focuses on type juggling and strict comparison. Understanding the difference between checking just the value (==) versus checking both value and data type (===) is crucial for avoiding unexpected bugs.
3. What are PHP Superglobals?
Questions about Superglobals (like $_GET, $_POST, $_SESSION, $_SERVER) are constantly searched because they are the primary way PHP interacts with user input, forms, and the server environment.
4. How do you handle file uploads securely in PHP?
Given the security risks associated with file uploads, developers frequently look up the proper use of functions like move_uploaded_file() and necessary validation checks.
5. Explain the difference between include(), require(), include_once(), and require_once().
These are fundamental functions for managing and structuring code by including external files. Knowing the difference, especially how require handles errors (fatal error) versus include (warning), is vital.
6. What are Traits in PHP?
With PHP's focus on Object-Oriented Programming (OOP), questions about Traits—a mechanism for code reuse that overcomes single inheritance limitations—are highly searched by intermediate developers.