PHP 8 Revealed: Use Attributes, the JIT Compiler, Union Types, and More for Web Development​

© The Author(s), under exclusive license to APress Media, LLC, part of Springer Nature 2021

G. EngebrethPHP 8 Revealedhttps://doi.org/10.1007/978-1-4842-6818-6_2

2. Union Types V2

Gunnard Engebreth¹  

(1)

Madison, WI, USA

 

Date: 2019-09-02

Author: Nikita Popov

Vote: 61/5

While union types can incur higher type checking cost they also provide more powerful means to help type inference and improve performance. As opcache improves over time I think we can expect the cost to decrease while the gain increases.

—Dik Takken

A union type accepts values of multiple different types, rather than a single one. PHP already supports two special union types:

• Type or null, using the special ?Type syntax.

• array or Traversable, using the special iterable type.

In previous versions ...