PHP concepts interview questions — Medium
149 medium-level PHP concepts questions from our PHP bank, each with the correct answer and an explanation of why it is correct.
What this covers
PHP concepts appears throughout PHP interviews. At medium level, interviewers are typically checking that you have used it in practice: what you configured, what broke, and how you knew it worked. Work through these, then explain your answer out loud; the second part is what interviews actually test.
20 example questions
1. In PHP, what is the idiomatic approach to null handling (how absence of a value is represented)?
- A. It is handled automatically by the garbage collector.
- B. It compiles to no-op.
- C. It always returns null.
- D. Use the language's idiomatic null handling feature, which is designed for exactly this purpose.correct
Why: Idiomatic PHP provides a built-in mechanism for null handling; relying on it (how absence of a value is represented) is clearer and safer than the alternatives, which misstate how PHP behaves.
2. Which option correctly describes function definition in PHP, specifically how reusable functions are declared?
- A. Use the language's idiomatic function definition feature, which is designed for exactly this purpose.correct
- B. It blocks the main thread until completion.
- C. It allocates a new copy every time.
- D. It is identical to the global variant.
Why: Idiomatic PHP provides a built-in mechanism for function definition; relying on it (how reusable functions are declared) is clearer and safer than the alternatives, which misstate how PHP behaves.
3. In PHP, what is the idiomatic approach to variable scoping (how block vs function scope affects visibility)?
- A. Use the language's idiomatic variable scoping feature, which is designed for exactly this purpose.correct
- B. It is identical to the global variant.
- C. It always returns null.
- D. It is undefined behavior.
Why: Idiomatic PHP provides a built-in mechanism for variable scoping; relying on it (how block vs function scope affects visibility) is clearer and safer than the alternatives, which misstate how PHP behaves.
4. When working with data serialization in PHP, which statement best reflects how data is serialized to a portable format?
- A. It compiles to no-op.
- B. Use the language's idiomatic data serialization feature, which is designed for exactly this purpose.correct
- C. It is undefined behavior.
- D. It throws a runtime exception by default.
Why: Idiomatic PHP provides a built-in mechanism for data serialization; relying on it (how data is serialized to a portable format) is clearer and safer than the alternatives, which misstate how PHP behaves.
5. Which option correctly describes generics in PHP, specifically how code is parameterized over types?
- A. It throws a runtime exception by default.
- B. It blocks the main thread until completion.
- C. Use the language's idiomatic generics feature, which is designed for exactly this purpose.correct
- D. It is only available in unsafe mode.
Why: Idiomatic PHP provides a built-in mechanism for generics; relying on it (how code is parameterized over types) is clearer and safer than the alternatives, which misstate how PHP behaves.
6. For a PHP codebase, what should you know about type system — how types are checked and inferred?
- A. It silently ignores the operation.
- B. It is identical to the global variant.
- C. It requires an external framework.
- D. Use the language's idiomatic type system feature, which is designed for exactly this purpose.correct
Why: Idiomatic PHP provides a built-in mechanism for type system; relying on it (how types are checked and inferred) is clearer and safer than the alternatives, which misstate how PHP behaves.
7. A reviewer asks about pattern matching in your PHP code. What is the correct guidance regarding how values are destructured by shape?
- A. It silently ignores the operation.
- B. Use the language's idiomatic pattern matching feature, which is designed for exactly this purpose.correct
- C. It is only available in unsafe mode.
- D. It blocks the main thread until completion.
Why: Idiomatic PHP provides a built-in mechanism for pattern matching; relying on it (how values are destructured by shape) is clearer and safer than the alternatives, which misstate how PHP behaves.
8. For a PHP codebase, what should you know about module system — how code is organized into modules or packages?
- A. It allocates a new copy every time.
- B. It is deprecated in current versions.
- C. Use the language's idiomatic module system feature, which is designed for exactly this purpose.correct
- D. It silently ignores the operation.
Why: Idiomatic PHP provides a built-in mechanism for module system; relying on it (how code is organized into modules or packages) is clearer and safer than the alternatives, which misstate how PHP behaves.
9. A reviewer asks about memory management in your PHP code. What is the correct guidance regarding how memory is allocated and reclaimed?
- A. It requires an external framework.
- B. Use the language's idiomatic memory management feature, which is designed for exactly this purpose.correct
- C. It compiles to no-op.
- D. It is only available in unsafe mode.
Why: Idiomatic PHP provides a built-in mechanism for memory management; relying on it (how memory is allocated and reclaimed) is clearer and safer than the alternatives, which misstate how PHP behaves.
10. A reviewer asks about immutability in your PHP code. What is the correct guidance regarding how immutable values are declared and enforced?
- A. It compiles to no-op.
- B. Use the language's idiomatic immutability feature, which is designed for exactly this purpose.correct
- C. It is deprecated in current versions.
- D. It throws a runtime exception by default.
Why: Idiomatic PHP provides a built-in mechanism for immutability; relying on it (how immutable values are declared and enforced) is clearer and safer than the alternatives, which misstate how PHP behaves.
11. When working with string handling in PHP, which statement best reflects how strings are represented and manipulated?
- A. Use the language's idiomatic string handling feature, which is designed for exactly this purpose.correct
- B. It silently ignores the operation.
- C. It compiles to no-op.
- D. It is identical to the global variant.
Why: Idiomatic PHP provides a built-in mechanism for string handling; relying on it (how strings are represented and manipulated) is clearer and safer than the alternatives, which misstate how PHP behaves.
12. Which option correctly describes concurrency model in PHP, specifically how concurrent or parallel work is expressed?
- A. It throws a runtime exception by default.
- B. It allocates a new copy every time.
- C. It silently ignores the operation.
- D. Use the language's idiomatic concurrency model feature, which is designed for exactly this purpose.correct
Why: Idiomatic PHP provides a built-in mechanism for concurrency model; relying on it (how concurrent or parallel work is expressed) is clearer and safer than the alternatives, which misstate how PHP behaves.
13. For a PHP codebase, what should you know about dependency management — how third-party libraries are added?
- A. It is only available in unsafe mode.
- B. It is handled automatically by the garbage collector.
- C. Use the language's idiomatic dependency management feature, which is designed for exactly this purpose.correct
- D. It throws a runtime exception by default.
Why: Idiomatic PHP provides a built-in mechanism for dependency management; relying on it (how third-party libraries are added) is clearer and safer than the alternatives, which misstate how PHP behaves.
14. For a PHP codebase, what should you know about closures and capture — how surrounding state is captured by inner functions?
- A. Use the language's idiomatic closures and capture feature, which is designed for exactly this purpose.correct
- B. It is identical to the global variant.
- C. It is only available in unsafe mode.
- D. It throws a runtime exception by default.
Why: Idiomatic PHP provides a built-in mechanism for closures and capture; relying on it (how surrounding state is captured by inner functions) is clearer and safer than the alternatives, which misstate how PHP behaves.
15. In PHP, what is the idiomatic approach to asynchronous I/O (how non-blocking I/O is performed)?
- A. It is deprecated in current versions.
- B. Use the language's idiomatic asynchronous I/O feature, which is designed for exactly this purpose.correct
- C. It blocks the main thread until completion.
- D. It silently ignores the operation.
Why: Idiomatic PHP provides a built-in mechanism for asynchronous I/O; relying on it (how non-blocking I/O is performed) is clearer and safer than the alternatives, which misstate how PHP behaves.
16. Which option correctly describes testing approach in PHP, specifically the conventional unit-testing approach?
- A. It silently ignores the operation.
- B. It blocks the main thread until completion.
- C. Use the language's idiomatic testing approach feature, which is designed for exactly this purpose.correct
- D. It is deprecated in current versions.
Why: Idiomatic PHP provides a built-in mechanism for testing approach; relying on it (the conventional unit-testing approach) is clearer and safer than the alternatives, which misstate how PHP behaves.
17. A reviewer asks about performance tuning in your PHP code. What is the correct guidance regarding the most effective optimization strategy?
- A. It is undefined behavior.
- B. It blocks the main thread until completion.
- C. Use the language's idiomatic performance tuning feature, which is designed for exactly this purpose.correct
- D. It allocates a new copy every time.
Why: Idiomatic PHP provides a built-in mechanism for performance tuning; relying on it (the most effective optimization strategy) is clearer and safer than the alternatives, which misstate how PHP behaves.
18. When working with error handling in PHP, which statement best reflects the recommended way to handle and propagate errors?
- A. Use the language's idiomatic error handling feature, which is designed for exactly this purpose.correct
- B. It is handled automatically by the garbage collector.
- C. It always returns null.
- D. It throws a runtime exception by default.
Why: Idiomatic PHP provides a built-in mechanism for error handling; relying on it (the recommended way to handle and propagate errors) is clearer and safer than the alternatives, which misstate how PHP behaves.
19. In PHP, what is the idiomatic approach to collection iteration (the idiomatic way to iterate a collection)?
- A. Use the language's idiomatic collection iteration feature, which is designed for exactly this purpose.correct
- B. It compiles to no-op.
- C. It silently ignores the operation.
- D. It requires an external framework.
Why: Idiomatic PHP provides a built-in mechanism for collection iteration; relying on it (the idiomatic way to iterate a collection) is clearer and safer than the alternatives, which misstate how PHP behaves.
20. When working with equality semantics in PHP, which statement best reflects the difference between identity and value equality?
- A. It requires an external framework.
- B. It silently ignores the operation.
- C. It is deprecated in current versions.
- D. Use the language's idiomatic equality semantics feature, which is designed for exactly this purpose.correct
Why: Idiomatic PHP provides a built-in mechanism for equality semantics; relying on it (the difference between identity and value equality) is clearer and safer than the alternatives, which misstate how PHP behaves.