PHP - Manual: First class callable syntax

2024-12-22

First class callable syntax

The first class callable syntax is introduced as of PHP 8.1.0, as a way of creating anonymous functions from callable. 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.

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

示例 #1 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'](...);
?>

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

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

示例 #2 Scope comparison of CallableExpr(...) 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
?>

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

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

<?php $obj?->method(...); $obj?->prop->method(...); ?>

add a note

User Contributed Notes

There are no user contributed notes for this page.

官方地址：https://www.php.net/manual/en/functions.first_class_callable_syntax.php

有任何技术问题请点击这里网站运营推广招聘

IT PHP 编程语言 Linux 开发编程科技 Elasticsearch HTML/CSS/XML 网络数据库 JAVA 面试 NoSQL C/C++ Golang Git 算法操作系统正则表达式 Redis 互联网 MySql JavaScript 运维软件国际架构设计 Mac OS TCP/IP Excel Vim Windows Socket Oracle VR MongoDB Python 运营 MemCache 商业硬件电子娱乐设计 nginx 摄影游戏 WordPress HTTP 团建数码电器

php7 安装fileinfo扩展 preg_split — 通过一个正则表达式分隔字符串 php位值,解决 PHP 中 usort 在值相同时改变原始位置的问题 [PHP] inet_pton/inet_ntop IP地址转换函数 [鸟哥]PHP_INT_MIN 和 -9223372036854775808 PHP 8.1 ADORecordSet对象 adodb手册 opcache预加载 Composer的Packagist资源 array_multisort() 多字段排序 PHPMailer设置utf8 PHPMailer字符集CharSet mysql面试题 php中几种注释规范 PHP json解析（json_decode）页面工具纯php实现DES以及TripleDES加密算法 [原创]诡异的php-fpm超时问题 php上周一、本周一、下周一日期 php扩展开发 Packagist / Composer 中国全量镜像

略微加速

PHP官方手册 - 互联网笔记

First class callable syntax

User Contributed Notes