带数组的双美元变量 [英] Double dollar variables with arrays

问题描述

我正在尝试使用双美元语法访问数组的第一项，但它无法像我希望的那样工作.

I am trying to access the first item of an array using the double dollar syntax, but it doesn't work as I would want it to.

<?php

$a = 'test';
$test = ['a', 'b'];
echo $$a[0];

这会说变量 t 未定义，因为它首先呈现 $a[0](这是一个t")，然后尝试访问名为 $t 的变量作为结果.

This will say that the variable t is undefined, because it renders the $a[0] first (which is a "t") and then tries to access the variable called $t as a result.

我想要的是与这些类似的东西(以下代码片段都不起作用，它们只是我尝试过的东西，以说明这个想法)

What I want is something along the line of these (none of the following snippets work, they are just things I tried, to illustrate the idea)

<?php

$a = 'test';
$test = ['a', 'b'];
echo {$$a}[0];

或者

<?php

$a = 'test';
$test = ['a', 'b'];
echo ${$$a}[0];

基本上，告诉 PHP $$a 部分优先.

Basically, tell PHP that the $$a part gets priority.

推荐答案

你们非常接近.您需要告诉 PHP 单独评估 $a .试试:

You were very close. You need to tell PHP to evaluate the $a alone. Try:

<?php

$a = 'test';
$test = ['a', 'b'];
echo ${$a}[0];

示例

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