[RESOLVED] Variable Variables or Variable Arrays in functions

[unlucky17]

For starters, I know that variable variables don't work in functions (which is really a shame), but I thought I read somewhere that you could use the same concept but replace it with an array. So, I wrote up some code that should work just fine, but it seems like it's hitting the same problem as variable variables - once they're in a function it just doesn't work at all, which is a shame because I can save myself hundreds of lines of code if I can get this to work.

So here's the deal: I have a function return a string. Then, I pass that into another function and it's supposed to plant that returned string into an array to get a result. This snippet of code is just a replica of the real thing, so it's not meant to be very efficient on it's own.

<?php

$name = array();
$name['j'] = "John";
$name['d'] = "Dave";
$name['w'] = "Will";

function select_person()
  {
  $select = rand(1,3);

  if ($select == 1)
    {
    return j;
    }

  if ($select == 2)
    {
    return d;
    }

  if ($select == 3)
    {
    return w;
    }
  } // End Function

// SAVE RESULT AS A VARIABLE AND PASS IT INTO ANOTHER FUNCTION LATER

$sp = select_player();

function display_name($var)
{
echo $name["$var"];
}

// PASS $SP INTO THIS FUNCTION, SO IT'S THE SAME AS PASSING J, D or W RATHER THAN PASSING THE VARIABLE.  IF YOU ECHO WHAT'S PASSED IN, IT ECHOES PROPERLY.

display_name("$sp");


?>

Please let me know if there's something I can do, because if this cannot be done at all then I will be VERY pissed off.

(By the way, this code works just fine if you don't run it within a function.)

[unlucky17]

Oh, by the way I edited this code from the original, so there's a function called "select_player()" that is supposed to be named "select_person()".

I guess you can't edit posts here, either?

[Kudose]

You can edit posts, you just don't have enough posts to do so yet.

In regards to your code, you cannot access $name inside display_name because it is not in the proper scope. $name is in the global scope and is not accessible within the display_name scope without being passed as a parameter or included using [man]global[/man] which you should not use.

Here is your code, a little simpler.

<?php

    $names = array('j' => 'John', 'd' => 'Dave', 'w' => 'Will');

    function select_person($array){
            return $array[array_rand($array)]; // this returns a random element from the given array
    }

    echo select_person($names);

edit, or you can use the two function way like you have

<?php

    $names = array('j' => 'John', 'd' => 'Dave', 'w' => 'Will');

    function select_person($array){
            return $array[array_rand($array)];
    }

    function display_random_person($names){
            echo select_person($names);
    }

    echo display_random_person($names);

[unlucky17]

Kudose;10919323 wrote:

You can edit posts, you just don't have enough posts to do so yet.

In regards to your code, you cannot access $name inside display_name because it is not in the proper scope. $name is in the global scope and is not accessible within the display_name scope without being passed as a parameter or included using [man]global[/man] which you should not use.

Here is your code, a little simpler.

<?php

    $names = array('j' => 'John', 'd' => 'Dave', 'w' => 'Will');

    function select_person($array){
            return $array[array_rand($array)]; // this returns a random element from the given array
    }

    echo select_person($names);

That code is simpler, but it's not going to do what I need it to do. I actually need to run a random number generator so each array (element? value?) has a different probability of being selected. In this code each has an equal probability. This code is merely an example of what I'm running. The full code is much more sophisticated.

So, I'm also assuming that "register_globals" has to be turned on to declare the array global in the code that I posted? Isn't that a security risk?

Also, why is it that you can use variable variables outside a function but not within? Does it have to do with the amount of work the virtual machine has to do to parse all of that? I'm getting really annoyed with all of the things I can't do in functions that would save me hundreds, if not thousands of lines of code.

[Kudose]

No, register_globals turns the superglobals into global variables, #edit# and yes, register_globals is a security risk.

The global keyword allows a global variable to be used within a function's scope.

In regards to variable variables, I'm not sure what you mean. Can you show me how you are using them? I can use them fine.

<?php

    function hello(){
            echo 'world'."\n";
    }

    function test(){
            $val = 'hello';
            $val();
    }

    function test2(){
            $a = 'c';
            $c = 'afk';
            $b = $$a;
            echo $b;
    }

    test();

    test2();

[unlucky17]

Kudose;10919330 wrote:

No, register_globals turns the superglobals into global variables, #edit# and yes, register_globals is a security risk.

The global keyword allows a global variable to be used within a function's scope.

In regards to variable variables, I'm not sure what you mean. Can you show me how you are using them? I can use them fine.

<?php

    function hello(){
            echo 'world'."\n";
    }

    function test(){
            $val = 'hello';
            $val();
    }

    function test2(){
            $a = 'c';
            $c = 'afk';
            $b = $$a;
            echo $b;
    }

    test();

    test2();

This was basically the context in which they were being used:

<?php

$whatever = 'correct output';

    function test2(){
            $var = 'whatever';
            $b = $$var;
            echo $b;
    }

    test2(); 

?>

[unlucky17]

In other words, all of the variables I am manipulating are declared and set outside of the function that needs to use them as variable variables. I have a long list of variables (or array values.. whichever) that need to be manipulated by several different functions, thus the point of using variable variables comes up so I don't have to make 10 functions that all do 1 thing.. I'd rather have 2 functions that do 10 things (one function to spit out the string that I can use dynamically, and the other to take that variable and modify whichever one it eventually references).

It even says on PHP.net that they cannot be used in class methods, functions and that the $this variable cannot be referenced dynamically.

[Kudose]

I think you misread the manual.

It says that Superglobals cannot be used in this way within functions or class methods and that the $this class variable cannot be accessed this way either.

Superglobals are $GLOBALS, $SERVER, $POST, $GET, $COOKIE, $SESSION, $FILES, $REQUEST and $ENV

To do what you are trying to do, you would use:

$whatever = 'correct output';
function test(){
  global $whatever;
  $var = 'whatever';
  $b = $$var;
  echo $b
}
test();

[Kudose]

What the manual is saying is this is illegal:

function test(){
  $var = '_SERVER';
  echo $$var['DOCUMENT_ROOT'];
}
test();

[Bjom]

You don't need variable variables at all. Arrays work just fine.

You don't need global variables either. Just pass everything needed between functions as arguments.

It's better practice to have a function just handle one thing and put them together in a structured way.

There is no imaginable reason why it should be impossible per se, to code what you want to in a class.

It would be easier to help if you could post the actual code.

Bjom

P.S.: sounds a bit harsh, I'm in a hurry. sry 🙂

[unlucky17]

Ohhhhh, I got it. That makes sense now.

I took that first block of code I posted and declared $name to be referenced as a global within the function and it worked just fine.

Nice, thanks for the help. To be honest I'm pretty new at coding and never had to declare whether to use a global or a local variable, so my function was searching for stuff that didn't exist.

Very much appreciated. You don't know how much work this saves me. 😃

[unlucky17]

Bjom;10919342 wrote:

You don't need variable variables at all. Arrays work just fine.

You don't need global variables either. Just pass everything needed between functions as arguments.

It's better practice to have a function just handle one thing and put them together in a structured way.

There is no imaginable reason why it should be impossible per se, to code what you want to in a class.

It would be easier to help if you could post the actual code.

Bjom

P.S.: sounds a bit harsh, I'm in a hurry. sry 🙂

Yeah, I am planning on using an array. Less coding. 🙂

I just needed to tell the function to look for that particular variable on a global scope, and it works just fine.

[Kudose]

You're very welcome.

Enjoy PHP. 😉