PHP：list（）在PhpStorm中给出未使用的局部变量错误

Question

I am using the answer found at https://stackoverflow.com/a/25749660 in order to sort the $_SERVER['HTTP_ACCEPT_LANGUAGE'] array by the most preferred language.

In that answer (which is working great by the way), one line is:

list($a, $b) = explode('-', $match[1]) + array('', '');

Within PhpStorm, I get the following error for that line:

"Unused local variable $b: The value of the variable is overwritten immediately".

I'm a little confused as to what this line is doing exactly, so I don't know if I should just keep it the same, or if I should modify it to:

list($a) = explode('-', $match[1]) + array('', '');

... which also seems to be working fine.

Should it be changed?

Answer 1

You can't join arrays with the arithmetic operator +. Basically you are telling PHP to convert the arrays to scalar types and then sum them, which yields you a number (probably arrays evaluate to 1 if it has elements and 0 if it doesn't).

The result is that effectively you are doing something like:

list($a, $b) = 2;

And the conclusion PHP reaches is that you haven't specified enough elements to define all the variables in the list.

To join two arrays together, use array_merge().

list($a, $b) = array_merge(explode('-', $match[1]), array('', ''));