Type restrictions for PHP function parameters

PHP function parameters can specify type restrictions to limit the function to only receive specific types of data, including: bool, int, float, string, array, object, callable, iterable. This restriction improves code readability and maintainability, and prevents arguments of mismatched types by raising a TypeError exception.

Type restrictions of PHP function parameters

In PHP, you can specify type restrictions for function parameters to limit the functions that can only Receive data of a specific type. This helps improve code readability and maintainability.

Syntax

function functionName(type $paramName) {
    // ...
}

Type

PHP supports the following types:

• bool: Boolean value
• int: Integer
• float: Floating point number
• string: String
• array: Array
• object: Object
• callable: Anonymous Function or closure
• iterable: any iterable object (such as array, object)

Practical case

The following is a function that verifies the user's email address:

function validateEmail(string $email): bool {
    return filter_var($email, FILTER_VALIDATE_EMAIL);
}

This function can only accept string parameters and performs email verification on them. If the argument provided is not a string, a TypeError exception will be raised.

Notes

• Type qualifiers are optional. If not specified, the function will accept any type of data.
• Type restrictions can only be used in function definitions. Cannot specify type in function call.
• If the provided parameters do not match the specified type, a TypeError exception will be raised.
• You can use union types (such as string|int) to specify that the function can accept multiple types.
• It is recommended to use type restrictions when possible to improve code reliability and debuggability.

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