In object oriented PHP, what type of inheritance does the language support for classes and how many parent classes can a class extend?

Introduction / Context:
Inheritance is a core concept in object oriented programming. It allows one class to reuse and extend the behaviour of another. Different languages implement inheritance in different ways. Some support multiple inheritance, where a class can extend more than one parent, while others restrict classes to a single parent and offer interfaces or traits for additional reuse. This question focuses on the type of inheritance that PHP supports for classes and how many parent classes a single class can extend.

Given Data / Assumptions:

• PHP supports object oriented programming with classes, interfaces, and traits.
• The syntax for inheritance uses the extends keyword for classes and implements for interfaces.
• PHP aims to balance flexibility with simplicity and avoid some of the complexity of full multiple inheritance.
• We are specifically discussing inheritance between classes, not interfaces or traits.

Concept / Approach:
PHP implements single inheritance for classes. That means any given class can extend at most one parent class. The child class inherits properties and methods from that parent and can override or add new ones. To achieve reuse across more than one source, PHP provides interfaces, which a class can implement in multiple, and traits, which allow horizontal code reuse. However, the actual class inheritance hierarchy remains a single chain, avoiding problems such as the diamond inheritance issue that can arise in languages with multiple class inheritance.

Step-by-Step Solution:
Step 1: Recall the basic syntax class Child extends Parent, which indicates that Child inherits from one Parent class.Step 2: Recognise that PHP does not allow syntax like class Child extends Parent1, Parent2, so you cannot directly inherit from multiple classes.Step 3: Note that PHP does allow multiple interfaces with implements, for example class Child extends Parent implements InterfaceA, InterfaceB.Step 4: Understand that traits provide code reuse via the use keyword, but they do not change the single inheritance rule for actual class ancestry.Step 5: Conclude that PHP supports single inheritance for classes, with each class having at most one direct parent class.

Verification / Alternative check:
You can verify the restriction by trying to write a PHP class that extends two different parents using more than one extends clause. The interpreter will report a syntax error. Documentation on PHP object model explicitly states that a class can only extend one other class. Examples in the manual show multiple interface implementation and trait usage alongside single class inheritance, which supports the conclusion that the language follows a single inheritance model for classes.

Why Other Options Are Wrong:
Option B claims that PHP supports full multiple inheritance for classes, which is incorrect and would require different syntax. Option C says PHP does not support inheritance at all, contradicting the existence of extends and the hierarchy features used across many frameworks. Option D suggests that inheritance is allowed only for interfaces and not for classes, but interfaces use implements and represent contracts rather than class inheritance itself. These statements do not match actual PHP behaviour.

Common Pitfalls:
A common pitfall is trying to simulate multiple inheritance by building very deep hierarchies or by misusing traits as if they were full parent classes. This can lead to hard to understand class structures. A better pattern is to keep the core class hierarchy simple, use interfaces to define contracts, and use traits to share reusable pieces of behaviour when necessary. Understanding the single inheritance rule helps developers design cleaner and more maintainable object oriented PHP architectures.

Final Answer:
Correct answer: PHP supports single inheritance for classes, where each class can extend only one parent class