Type declarations for parameters in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a type declaration for a parameter in PHP?

A type declaration for a parameter in PHP specifies the expected data type of the argument passed to a function or method. It helps catch errors early by ensuring the correct type is used.

beginner

How do you declare a parameter to accept only integers in PHP?

You add the type before the parameter name, like this: <code>function example(int $number) { }</code>. This means the function expects an integer argument.

intermediate

What happens if you pass a wrong type to a function with a declared parameter type in PHP?

PHP will throw a TypeError at runtime, stopping the program unless caught. This helps prevent bugs caused by wrong data types.

intermediate

Can you declare a parameter to accept multiple types in PHP?

Yes, since PHP 8.0, you can use union types like <code>function example(int|string $value) { }</code> to accept either an integer or a string.

beginner

What is the difference between type declarations and type hints in PHP?

They mean the same thing: specifying the expected type of a parameter. The term 'type hint' was used before PHP 7, now 'type declaration' is more common.

How do you declare a function parameter to accept only strings in PHP?

A function example(string $text) {}

B function example($text: string) {}

C function example(text string) {}

D function example($text) : string {}

The correct syntax is to put the type before the parameter name: string $text.

What error does PHP throw if a wrong type is passed to a typed parameter?

A TypeError

B SyntaxError

C ValueError

D RuntimeException

PHP throws a TypeError when a parameter type declaration is violated.

Which PHP version introduced union types for parameters?

A PHP 7.4

B PHP 5.6

C PHP 7.0

D PHP 8.0

Union types were introduced in PHP 8.0, allowing multiple types for a parameter.

What does this function declaration mean? function test(array $data) {}

A The function accepts any type of argument.

B The function accepts only arrays as argument.

C The function returns an array.

D The function accepts only strings.

The parameter $data must be an array due to the type declaration.

Can you omit the type declaration for a parameter in PHP?

A Only in PHP 8 and above.

B No, all parameters must have a type declaration.

C Yes, parameters can be untyped and accept any value.

D Only for class methods.

Type declarations are optional; if omitted, the parameter accepts any type.

Explain how type declarations for parameters improve PHP code quality.

Think about how telling PHP what type to expect helps avoid mistakes.

Describe how to declare a parameter that accepts either an integer or a string in PHP.

Use the vertical bar | to separate types.