{"id":2054,"date":"2021-06-27T09:10:15","date_gmt":"2021-06-27T09:10:15","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=2054"},"modified":"2021-06-27T09:10:43","modified_gmt":"2021-06-27T09:10:43","slug":"php-__invoke","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-oop\/php-__invoke\/","title":{"rendered":"PHP __invoke"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the PHP __invoke()<\/code> magic method and how to use it effectively.<\/p>\n\n\n\n

Introduction to the PHP __invoke() magic method #<\/a><\/h2>\n\n\n\n

Suppose that you have a class<\/a> called MyClass<\/code>:<\/p>\n\n\n

class<\/span> MyClass<\/span> \n<\/span>{\n    \/\/ ...<\/span>\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Typically, you create a new instance of the MyClass<\/code> and access its methods and properties like this:<\/p>\n\n\n
$instance = new<\/span> MyClass();\n$instance->methodName();<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
MyClass::staticMethod();<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
$instance($arguments);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this case, PHP will call the __invoke()<\/code> method of the MyClass<\/code>. For example:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> MyClass<\/span>\n<\/span>{\n    public<\/span> function<\/span> __invoke<\/span>(...$arguments)<\/span>\n    <\/span>{\n        echo<\/span> 'Called to the __invoke method'<\/span>;\n    }\n}\n\n$instance = new<\/span> MyClass;\n$instance();<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Called to the __invoke method<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The $instance<\/code> is known as a function object or functor.<\/p>\n\n\n\n
The __invoke()<\/code> magic method has the following syntax:<\/p>\n\n\n
__invoke( ...$values): mixed<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
PHP will call the __invoke()<\/code> magic method when you call an object as a function.<\/p>\n\n\n\n
Also, the object of the class that implements the __invoke()<\/code> magic method is a callable. For example:<\/p>\n\n\n
echo<\/span> is_callable($instance) ? 'yes'<\/span> : 'no'<\/span>; \/\/ yes<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the $instance<\/code> of the MyClass is a callable. This means that you can pass it to any function or method that accepts a callable.<\/p>\n\n\n\n
Practical PHP __invoke() magic method example #<\/a><\/h2>\n\n\n\n
Suppose that you have an array<\/a> of customer data like this;<\/p>\n\n\n
$customers = [\n    ['id'<\/span> => 1<\/span>, 'name'<\/span> => 'John'<\/span>, 'credit'<\/span> => 20000<\/span>],\n    ['id'<\/span> => 3<\/span>, 'name'<\/span> => 'Alice'<\/span>, 'credit'<\/span> => 10000<\/span>],\n    ['id'<\/span> => 2<\/span>, 'name'<\/span> => 'Bob'<\/span>, 'credit'<\/span> => 15000<\/span>]\n];<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
To sort the customers by name or credit, you can use the usort()<\/code> function. The second parameter of the usort()<\/code> function is a callable that determines the sort order:<\/p>\n\n\n
usort(array<\/span> &$array, callable $callback): bool\r<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The following defines the class Comparator<\/code> that implements the __invoke()<\/code> magic method:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> Comparator<\/span>\n<\/span>{\n    private<\/span> $key;\n\n    public<\/span> function<\/span> __construct<\/span>(string $key)<\/span>\n    <\/span>{\n        $this<\/span>->key = $key;\n    }\n\n    public<\/span> function<\/span> __invoke<\/span>($a, $b)<\/span>\n    <\/span>{\n        return<\/span> $a[$this<\/span>->key] <=> $b[$this<\/span>->key];\n    }\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The __invoke()<\/code> method returns the result of the comparison of two array elements by a specified key.<\/p>\n\n\n\n
To use the Comparator<\/code> class, you can create a new instance of the class and pass it to the usort()<\/code> function as follows:<\/p>\n\n\n
usort($customers, new<\/span> Comparator('name'<\/span>));<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
This statement sorts the customers by name.<\/p>\n\n\n\n
To sort the customers by credit, you can use the credit as the key like this:<\/p>\n\n\n
usort($customers, new<\/span> Comparator('credit'<\/span>));<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Put it all together.<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> Comparator<\/span>\n<\/span>{\n    private<\/span> $key;\n\n    public<\/span> function<\/span> __construct<\/span>(string $key)<\/span>\n    <\/span>{\n        $this<\/span>->key = $key;\n    }\n\n    public<\/span> function<\/span> __invoke<\/span>($a, $b)<\/span>\n    <\/span>{\n        return<\/span> $a[$this<\/span>->key] <=> $b[$this<\/span>->key];\n    }\n}\n\n$customers = [\n    ['id'<\/span> => 1<\/span>, 'name'<\/span> => 'John'<\/span>, 'credit'<\/span> => 20000<\/span>],\n    ['id'<\/span> => 3<\/span>, 'name'<\/span> => 'Alice'<\/span>, 'credit'<\/span> => 10000<\/span>],\n    ['id'<\/span> => 2<\/span>, 'name'<\/span> => 'Bob'<\/span>, 'credit'<\/span> => 15000<\/span>]\n];\n\n\/\/ sort customers by names<\/span>\nusort($customers, new<\/span> Comparator('name'<\/span>));\nprint_r($customers);\n\n\/\/ sort customers by credit<\/span>\nusort($customers, new<\/span> Comparator('credit'<\/span>));\nprint_r($customers);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
  • Use the __invoke()<\/code> magic method is invoked when you call an object as a function.<\/li>
  • An object of a class that implements the __invoke()<\/code> is known as a function object or functor. It’s also a callable.<\/li><\/ul>\n
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    Did you find this tutorial useful?<\/div>\n\t\t
    \n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t
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Besides using the MyClass<\/code> these ways, PHP allows you to use the object of the class as a function<\/a>. For example:<\/p>\n\n\n
Or if the MyClass<\/code> has static methods<\/a>, you can access them using the ::<\/code> operator:<\/p>\n\n\n