What are the main differences between PHP 7.4 and PHP 8.1 in terms of their functionality and new features?

The main differences between PHP 7.4 and PHP 8.1 are related to new features and performance improvements:

• PHP 7.4:

  • Typed properties introduced.
  • Arrow functions added for more concise syntax.
  • Null coalescing assignment operator (??=).
  • Performance and stability improvements.

• PHP 8.1:

  • Enums introduced — a new way to define sets of constants.
  • Readonly properties introduced.
  • Asynchronous generators and improvements in Fibers for asynchronous programming.
  • New functions and syntactic enhancements, such as first-class callable syntax.
  • Improvements in types, including intersection types.

Thus, PHP 8.1 extends the language capabilities, improves typing, and introduces new constructs that simplify development and make the code more expressive compared to PHP 7.4.