PHP，$ this-> {$ var} - 这是什么意思？ [英] PHP, $this->{$var} -- what does that mean?

问题描述

我遇到了访问/更改变量的需要：

I have encountered the need to access/change a variable as such:

$this->{$var}

上下文是使用CI数据图表获取规则。我似乎找不到这个语法实际上做什么。在这种情况下，我们做什么？为什么不只是：

The context is with CI datamapper get rules. I cant seem to find what this syntax actually does. What do the {'s do in this context? Why not just:

$this->var

感谢！

推荐答案

strong>，这样你最终会得到 $ this-> {value-of-$ val} 。

This is a variable variable, such that you will end up with $this->{value-of-$val}.

请参阅： http://php.net/manual/en/language.variables.variable.php

例如：

$this->a = "hello";
$this->b = "hi";
$this->val = "howdy";

$val = "a";
echo $this->{$val}; // outputs "hello"

$val = "b";
echo $this->{$val}; // outputs "hi"

echo $this->val; // outputs "howdy"

echo $this->{"val"}; // also outputs "howdy"

工作实例： http://3v4l.org/QNds9

这当然是在类上下文中工作。您可以在本地上下文中使用变量变量，就像这样：

This of course is working within a class context. You can use variable variables in a local context just as easily like this:

$a = "hello";
$b = "hi";

$val = "a";
echo $$val; // outputs "hello"

$val = "b";
echo $$val; // outputs "hi"

工作范例：http://3v4l.org/n16sk

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