New feature in PHP version 5.4: How to use callable type hint parameters to accept callable functions or methods

New features in PHP 5.4 version: How to use callable type hint parameters to accept callable functions or methods

Introduction:
PHP 5.4 version introduces a very convenient new feature - you can use callable types Prompt arguments to accept a callable function or method. This new feature allows functions and methods to directly specify corresponding callable arguments without additional checks and conversions. In this article, we will introduce the use of callable type hints and provide some code examples to help readers better understand.

What is the callable type?
In PHP, callable is a special data type used to represent a callable entity, such as a function or method. In a function or method definition, using callable type hint parameters ensures that the arguments passed to the function or method are callable.

Example 1: Use callable type to prompt function parameters

function invokeFunction(callable $callback) {
    $callback(); // 调用传递进来的可调用参数
}

function hello() {
    echo "Hello, World!";
}

invokeFunction('hello'); // 输出: Hello, World!

In example 1, we define a function invokeFunction(), which accepts a callable type parameter $callback. Inside the function body, we directly call the passed callable parameters by calling $callback().

Example 2: Using callable type hint method parameters

class Greeting {
    public function sayHello() {
        echo "Hello, World!";
    }
}

function invokeMethod($object, callable $method) {
    $method->call($object); // 在给定对象上调用传递进来的方法参数
}

$greeting = new Greeting();
$callback = [$greeting, 'sayHello'];

invokeMethod($greeting, $callback); // 输出: Hello, World!

In example 2, we define a class Greeting, which contains a method sayHello() . We also define a function invokeMethod(), which accepts an object and a callable type parameter $method. Inside the function body, we use the $method->call($object) syntax to call the passed method on the given object.

Summary:
By using callable type hint parameters, we can more conveniently accept callable functions or methods as actual parameters without the need for additional checks and conversions. This feature is very useful when designing and writing reusable code. I hope the above examples and explanations can help readers better understand and use the new features of callable type hint parameters.

Reference:

• PHP: Callable typehint - https://www.php.net/manual/en/language.types.callable.php

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