PHP Variable Variable in Function

Question

i've been wondering how this could be done, i've got a function.

  $sky = (a range of number 1 to 10);


function condi($nnn){ 
  if($$nnn <= 1){
  echo 'Fails';
  }
  elseif($$nnn <= 3){
  echo 'Respectable';
  }
  elseif($$nnn <= 5){
  echo 'Decent';
  }
  elseif($$nnn <= 7){
  echo 'Great';
  }
  elseif($$nnn <= 9){
  echo 'Legendary';
  }
  elseif($$nnn = 10){
  echo 'Ultimate';
  }
 }

  condi('sky');

But no matter what is the value of $sky, the output is fails.

So i decided to check what is the value of $$nnn, then i realized that the $$nnn doesn't have a value in it. Any help please?

If you really want a variable variable/dynamic variable you could write: ${$nnn} to make it more clear what you're really trying to do. — Robert de W
– Robert de W, Commented Jul 18, 2011 at 7:33

ThiefMaster · Accepted Answer · 2011-07-18 07:24:36Z

2

Replace $$nnn with $GLOBALS[$nnn].

Whatever variable name $nnn contains - it's not local to the function so you need to acess it via the $GLOBALS array (which is much cleaner than doing something like global $$nnn; and then using $$nnn).

answered Jul 18, 2011 at 7:24

ThiefMaster

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5 Comments

Rudi Visser Over a year ago

+1 I upvoted both this and global $$nnn; as they are both valid solutions, but you're right, this is cleaner (as long as the variable is brought to the inner scope, using $GLOBALS[$nnn] everywhere would be an eyesore :-)

Paul Over a year ago

@rudi_visser What's the difference between global $$nnn; and aliasing like $$nn = $GLOBALS[$nnn]; How is one cleaner than the other. I've been using global $o; to import global scoped variables (not that I use them much) for a long time :S

Crays Over a year ago

Thanks, still pretty new to PHP :) Works well!

Rudi Visser Over a year ago

@PaulPRO Some people see global as a (excuse me) bastardisation of programming like goto. I'm not exactly one of them, but where possible I do believe it is better to encapsulate functions that rely on external variables in classes of their own, where you can import everything you need in a way that makes sense. What I meant by aliasing the variable is doing something such as: function name($varname) { $var = $GLOBALS[$varname]; switch($var) { /* .. */ } } as it's simply cleaner. Variable-variables can be confusing at best of times.. But I think it's mainly down to personal preference :)

Rudi Visser Over a year ago

@PaulPro also of course, using GLOBALS allows you to have a variable called $$name (ie. $sky) internally aswell! But still, I think the key point is to avoid globals whereever possible.

Paul · Accepted Answer · 2011-07-18 07:23:26Z

2

$sky is in the global scope:

function condi($nnn){ 
  global $$nnn;
  if($$nnn <= 1){
    ...

answered Jul 18, 2011 at 7:23

Paul

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4 Comments

Robert de W Over a year ago

No, you're making it even worse. He doesn't want a global, he just wants to pass an argument to it's function (otherwise the 'function' would be no use).

Rudi Visser Over a year ago

@Robert He wants to pass a variable name to the function, and utilise that variable (in global scope) from within the function. It's a silly requirement, but this will resolve his issue.

Paul Over a year ago

@Robert de W How so? He is passing a string to a function which tells the function which global variable he wants to use.

Robert de W Over a year ago

@PaulPRO; You're right, he does. I made the above conclusion too soon in answering the question.

cHao · Accepted Answer · 2011-07-18 07:28:00Z

0

In order for the function to see $sky (which i'm presuming is the goal), it must be visible in the function's scope. Globals aren't visible by default.

You'll need to either say global $$nnn; inside your function, or change $$nnn to $GLOBALS[$nnn] instead. And note, this will only work for globals -- you won't be able to pass the names of other functions' locals and have this function see them.

answered Jul 18, 2011 at 7:28

cHao

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Comments

madflow · Accepted Answer · 2011-07-18 07:21:59Z

-1

You have two $$ signs in your "nnn" variable. Delete one.

answered Jul 18, 2011 at 7:21

madflow

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Comments

Mihai Iorga · Accepted Answer · 2011-07-18 07:32:40Z

-1

you should use

<?php
$sky = rand(1, 5);
function condi($nnn){
    global $sky;
    switch ($$nnn) {
        case $$nnn < 1:
            echo "Fails";
            break;
        case $$nnn < 3:
            echo "Respectable";
            break;
        case $$nnn <= 5:
            echo "Decent";
            break;
        // .................... //
    }
}
condi('sky');
?>

answered Jul 18, 2011 at 7:32

Mihai Iorga

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1 Comment

Paul Over a year ago

global $sky; defeats the purpose of a variable variable if you have to know what it's going to contain in advance.

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