不带引号PHP数组访问 [英] PHP Array access without quotes

问题描述

我敲到一个现象，在现有的PHP源代码，
有没有这样的撇号字段访问：$ _ GET [测试]

I knocked to a phenomenon in an existing php source, with field access without apostrophe like this: $_GET[test].

我不确定，也不知道，这是一个可能的方式，
所以我写了一个简单的例子来进行测试：

I got unsure, also don't know, that this is a possible way, so I wrote a short example for testing:

echo "Array Test, fields without apostrophe, like \$_GET[fieldname]<BR><BR>";
$a = array();
$a['test'] = "ArrayValue";
echo "case 1 -> \$a['test']: " . $a['test'] . "<BR>";
echo "case 2 -> \$a[\"test\"]: " . $a["test"] . "<BR>";
echo "case 3 -> \$a[test]: " . $a[test] . "<BR>";

和它的作品，每个结果得到的值（ArrayValue）。

And it works, every result got the value (ArrayValue).

我preFER样病例的访问方法2.

I prefer the access method like case 2.

时的情况下，3正常的，允许编码风格在PHP？

Is case 3 a normal, allowed coding style in php?

推荐答案

在这里会发生什么事，是PHP看到的恒定名为测试。如果定义常量，则返回其值，它是没有定义，PHP回落到字符串测试。例如：

What happens here, is that PHP sees a constant called test. If the constant is defined, the value is returned, it isn't defined, PHP falls back to the string "test". For example:

$array = array("A" => "Foo", "B" => "Bar", "C" => "Baz")
define("B", "C");

echo $array[A];   // The constant "A" is undefined, 
                  // so PHP falls back to the string "A", 
                  // which has the value "Foo".
echo $array["B"]; // The result is "Bar".
echo $array[B];   // The value of constant "B" is the string "C".
                  // The result is "Baz".

这是为了向下兼容，你永远不应该使用它。如果你打开声明，你会看到PHP抱怨关于它。

It's for backwards compatibility and you should never use it. If you'll turn on notices, you'll see that PHP complains about it.

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