Trying to access $_SERVER(or any global) variable from string name

Question

Today I met such a terrible situation. It seems this bug is related to PHP.

I'm trying to access to $_SERVER or another super global variables but from string name.

This version of implementation is working.

var_dump(${"_SERVER"}); // working

But when trying to do this with variable then receiving notice that variable not found.

$var_name = "_SERVER";
var_dump(${$var_name}); // Notice</b>:  Undefined variable: _SERVER in...

And this will happen only with a global variable.

What is going on there? Can someone explain this situation.

It not works for me. It output `null` when use `var_dump(${$var_name})`, but output everything of the session when use `var_dump($_SERSION)` — LF00, Nov 13 '19 at 07:32
@NigelRen you may as well still close it so that there's a reference link... — Nick, Nov 13 '19 at 07:56

LF00 · Accepted Answer · 2019-11-13T07:50:51.823

4

variable variables cannot be used with PHP's Superglobal arrays within functions or class methods. Demo

Refer to php doc Variable variables

Please note that variable variables cannot be used with PHP's Superglobal arrays within functions or class methods. The variable $this is also a special variable that cannot be referenced dynamically.

edited Nov 13 '19 at 07:50

answered Nov 13 '19 at 07:40

LF00

27,015
29
156
295

Trying to access $_SERVER(or any global) variable from string name

This version of implementation is working.

But when trying to do this with variable then receiving notice that variable not found.

1 Answers1

Linked