PHP function return type declarations can improve code clarity and robustness, especially for large projects and multi-person collaboration. By directly adding colons and types (such as: int, : string) after the function definition, the function can be forced to return data of the specified type. If the return value type does not match, an error will be thrown during runtime. Supported types include basic types, arrays, objects, callable objects, and union types starting from PHP 8 (such as: int|float). For cases where null may be returned, a ? prefix is ??available, such as: ?string. The return type declaration itself does not need to enable strict_types to take effect, but it is recommended to enable strict mode in a unified way to maintain the consistent code style. Best practices include trying to clarify the return type, using union types reasonably, and combining PHPDoc annotations to enhance readability and IDE support.

PHP's function return type declaration is actually quite practical, especially when the project becomes larger and multiple people collaborate, it can help you reduce many potential errors. Simply put, you can directly write down what type of data the function should return when defining a function, such as int , string , array , etc.

The benefits of doing this are obvious: the code is clearer, the IDE can better prompt, and the runtime can also force check whether the return value meets expectations (if it does not meet, an error will be reported). However, it should be noted that by default PHP is of weak type. These type declarations will only take effect after strict mode is enabled ( declare(strict_types=1); ); and return type declarations will be mandatory checked regardless of whether strict mode is enabled or not.

Here are a few points you may care about when using return type declarations:

How to correctly write a return type declaration

Just add a colon and type after the brackets of the function definition. The format is as follows:

 function getAge(): int {
    return 25;
}

Here : int is the return type declaration, indicating that this function must return an integer. If you accidentally return the string, PHP will throw an error at runtime.

Supported types include basic types (such as int , float , string , bool ), array array , object object , callable object callable , and Union types supported since PHP 8, such as:

 function getScore(): int|float {
    return 90.5;
}

Frequently Asked Questions and Notes

• What should I do if I return null?
  If your function may not return any value, remember to add ? , for example ?string means that it can return a string or null:

   function getName(): ?string {
      return null;
  }

• What should I do if the returned class or interface?
  You can write the class name or interface name directly as the return type:

   function getUser(): User {
      return new User();
  }

• Don't forget the impact of strict_types on return types
  In fact, the return type declaration itself does not need to enable strict_types , it does type check by default. However, in order to unify the style, it is recommended to add declare(strict_types=1); at the top of the file.

Best practices for returning type declarations

• Try to clarify the return type
  Even if you can omit type declarations to make the function more "flexible", in most business logic, explicit return types will actually make subsequent maintenance easier.

• Pay attention to order and readability when using union types
  For example, int|string and string|int are both legal, but logically it is best to put the most common types in front for easy reading.

• Use it better together with document comments
  Although the return type is already clear, adding PHPDoc is helpful, especially for IDE and team members:

   /**
   * Get user age*
   * @return int User's age*/
  function getAge(): int {
      return 25;
  }

  ---

  Basically that's it. Return type declarations are not a high-level trick, but they do make the code clearer, more robust, and not complicated to write. As long as you develop a habit, you will gradually find that the benefits it brings are more worthwhile than typing a few more words.

  The above is the detailed content of PHP function return type declarations. For more information, please follow other related articles on the PHP Chinese website!