What is a PHP trait?

A PHP trait is a mechanism for code reuse in single inheritance. Traits allow developers to create reusable sets of methods that can be included in one or more classes. This is particularly useful in PHP, which allows only single inheritance – meaning a class can extend only one parent class. Traits help to overcome this limitation by allowing the inclusion of methods from multiple traits into a single class, thus promoting code reuse and reducing redundancy.

By defining common functionality in traits, developers can share that behavior across different classes while maintaining the flexibility of single inheritance. This ability to compose classes from different behavioral building blocks is a powerful feature of PHP that facilitates better code organization and the implementation of the DRY (Don't Repeat Yourself) principle.

In the context of the other options, a trait is not a type of variable, it does not directly enhance performance in itself, nor is it a special kind of class created for object instantiation, which distinguishes its utility and functionality significantly from those incorrect interpretations.