PHP.nl

First class callable syntax

First class callable syntax

The first class callable syntax is introduced as of PHP 8.1.0, as a way of creating  from .
It supersedes existing callable syntax using strings and arrays.
The advantage of this syntax is that it is accessible to static analysis, and uses the scope at the point where the callable is acquired.

anonymous functionscallable

 syntax is used to create a  object from callable.  accepts any expression that can be directly called in the PHP grammar:

CallableExpr(...)``Closure``CallableExprVoorbeeld: Simple first class callable syntax

<?php

class Foo {
   public function method() {}
   public static function staticmethod() {}
   public function __invoke() {}
}

$obj = new Foo();
$classStr = 'Foo';
$methodStr = 'method';
$staticmethodStr = 'staticmethod';


$f1 = strlen(...);
$f2 = $obj(...);  // invokable object
$f3 = $obj->method(...);
$f4 = $obj->$methodStr(...);
$f5 = Foo::staticmethod(...);
$f6 = $classStr::$staticmethodStr(...);

// traditional callable using string, array
$f7 = 'strlen'(...);
$f8 = [$obj, 'method'](...);
$f9 = [Foo::class, 'staticmethod'](...);
?>

Opmerking: > The is part of the syntax, and not an omission. ...

 has the same semantics as .
That is, unlike callable using strings and arrays,  respects the scope at the point where it is created:

CallableExpr(...)``Closure::fromCallable``CallableExpr(...)Voorbeeld: Scope comparison of and traditional callable

<?php

class Foo {
    public function getPrivateMethod() {
        return [$this, 'privateMethod'];
    }

    private function privateMethod() {
        echo __METHOD__, "\n";
    }
}

$foo = new Foo;
$privateMethod = $foo->getPrivateMethod();
$privateMethod();
// Fatal error: Call to private method Foo::privateMethod() from global scope
// This is because call is performed outside from Foo and visibility will be checked from this point.

class Foo1 {
    public function getPrivateMethod() {
        // Uses the scope where the callable is acquired.
        return $this->privateMethod(...); // identical to Closure::fromCallable([$this, 'privateMethod']);
    }

    private function privateMethod() {
        echo __METHOD__, "\n";
    }
}

$foo1 = new Foo1;
$privateMethod = $foo1->getPrivateMethod();
$privateMethod();  // Foo1::privateMethod
?>

Opmerking: > Object creation by this syntax (e.g ) is not supported, because syntax is not considered a call. new Foo(...)``new Foo()

Opmerking: > The first-class callable syntax cannot be combined with the . Both of the following result in a compile-time error:

nullsafe operator```php
method(...); $obj?->prop->method(...); ?>
Vorige ← Arrow Functions

Documentatie