为什么不能在PHP 5.5.4中将$ this用作词法变量? [英] Why can I not use $this as a lexical variable in PHP 5.5.4?

问题描述

$ php --version
PHP 5.5.4 (cli) (built: Sep 19 2013 17:10:06) 
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2013 Zend Technologies

以下代码(类似于 https://bugs.php.net/bug.php?id上的示例= 49543 ):

class Foo
{
    public function bar()
    {
        return function() use ($this)
        {
            echo "in closure\n";
        };
    }
}

失败:

PHP Fatal error:  Cannot use $this as lexical variable

然而，根据PHP文档和Rasmus Lerdorf对该错误报告的评论，从PHP 5.4开始添加了$ this在匿名函数中.我在做什么错了?

Yet according to the PHP docs and a comment on that bug report from Rasmus Lerdorf, using $this in anonymous functions was added as of PHP 5.4. What am I doing wrong?

推荐答案

因此，如果未通过"use"关键字指定$ this，则似乎可以使用$ this.

So it seems $this can be used simply if it isn't specified via the "use" keyword.

以下回显"bar":

class Foo
{
    private $foo = 'bar';

    public function bar()
    {
        return function()
        {
            echo $this->foo;
        };
    }
}

$bar = (new Foo)->bar();

$bar();

这是在php-internals邮件列表中报告的，显然是由于5.3缺少对此功能的支持而造成的:

This was reported in the php-internals mailing list and is apparently overhang from 5.3's lack of support for this functionality:

http://marc.info/?l=php-internals&m=132592886711725

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