PHP Nullable types and function parameters

Question

I want to ask if both are the same and if not, where's the difference between them:

/**
 * @param int|null $id Any id.
 */
public function testSomething(int $id = null) {}

and

/**
 * @param int|null $id Any id.
 */
public function testSomething(?int $id) {}

Thank you for your answer!

the only difference I can see is that you _cannot_ invoke `testSomething(?int $id) {}` without arguments - will probably throw a fatal error, whereas you _can_ invoke the first case `testSomething(int $id = null) {}` without arguments. — jibsteroos, Sep 23 '20 at 12:33
Does this answer your question? [What is the purpose of the question marks before type declaration in PHP7 (?string or ?int)?](https://stackoverflow.com/questions/48450739/what-is-the-purpose-of-the-question-marks-before-type-declaration-in-php7-stri) — Nico Haase, Aug 19 '21 at 13:14

score 4 · Answer 1 · edited Aug 17 '22 at 08:54

It's different. The first function declaration :

public function testSomething(int $id = null) {}

sets the default value to null, if you call the function without an argument.

The second definition :

public function testSomething(?int $id) {}

will accept a null value as the first argument, but does not set it to a default value if the argument is missing. So you always need to have an argument if you call the function in the second way.

PHP Nullable types and function parameters

1 Answers1