Union types in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a union type in PHP?

A union type allows a variable or parameter to accept values of multiple specified types. It is written using the pipe symbol (|) between types.

beginner

How do you declare a function parameter that accepts either an int or a string using union types?

You declare it like this: <code>function example(int|string $param) { }</code>. This means $param can be an int or a string.

intermediate

Can union types include null in PHP? How?

Yes. You can include null in a union type like int|null. This means the value can be an int or null.

intermediate

What happens if a value passed to a union typed parameter does not match any of the types?

PHP will throw a TypeError at runtime because the value does not match the declared union types.

advanced

Can you use union types with class types in PHP?

Yes. You can declare a parameter or property to accept multiple class types like <code>ClassA|ClassB</code>. The value must be an instance of either class.

Which symbol is used to declare union types in PHP?

A :

B &

C ,

D |

The pipe symbol (|) is used to separate types in a union type declaration.

What will happen if you pass a float to a parameter declared as int|string?

A It will accept the float without error.

B It will throw a TypeError.

C It will convert the float to int automatically.

D It will ignore the parameter.

Passing a float to a parameter declared as int|string causes a TypeError because float is not allowed.

Can union types include the type 'null'?

A Yes, by including null in the union.

B No, null cannot be part of union types.

C Only if the type is nullable with ?.

D Only for class types.

You can include null explicitly in union types, like int|null.

Which PHP version introduced union types?

A PHP 8.0

B PHP 7.4

C PHP 8.1

D PHP 7.2

Union types were introduced in PHP 8.0.

Is this a valid union type declaration? function test(int|float|string $value) {}

A No, float cannot be in union types.

B No, only two types allowed in union.

C Yes, it accepts int, float, or string.

D Yes, but only in PHP 7.

Union types can include multiple types separated by |, so this is valid.

Explain what union types are in PHP and how to use them in function parameters.

Think about allowing multiple types for one variable.

Describe what happens if a value does not match any type in a union type declaration.

Consider PHP's behavior when types don't match.