使用变量变量名访问嵌套数组

Question

In php there is variable variable names :

As the example goes:

$a = 'hello';
$$a = 'world';

echo $hello; // outputs world

Now, we also have nested arrays:

$myvar = Array(
    'a' => Array('b' => 1, 'c' => 2),
    'd' => Array('e' => 3, 'f' => 4)
);

echo $myvar['a']['e']; // outputs e

Question: is it possible to access such array with variable names?

Something like the following:

$myvarname = 'myvar[a][e]';
echo $$myvarname;

If yes - how?

EDIT:

What I am trying to do is build an array in a loop. I have no idea about the incoming data, so array can be any level of depth.

There is a number of input rows formatted like this:

 /katalog/category1/subcategory1/subcategory2

I made a loop through input lines, and split the URLs with "/".

After that I am trying to build an array, which will represent the structure of all urls.

 category 1
 --> subcategory 1
     --> subcategory 2
     --> subcategory 3
         --> subcategory 4
 category 2
 --> subcategory 5
 category 3
 category 4

The main part of the question is how to use variable variable for nested array. If at all possible. I included the actual use case because it was asked from me how that can be used in real life. Don't need a solution to my problem - I can solve that question myself.

However, variable variable usage - that is the real question.

Answer 1

It could be done with eval() :

$myvarname = "myvar['a']['b']";
eval("\$result = \${$myvarname};");
var_dump($result);

Output:

int(1)

Demo

---

But using eval() is generally a bad idea, especially if this involves user input. The function allows arbitrary code to be executed - which means a user with malicious intent could execute harmful code on your server. This is just a POC and should not be used in production code.

Answer 2

I suggest using recursion to solve this problem. I wasn't 100% sure on the structure of the output, but hopefully this should be able to point you in the right direction:

function createArray($pieces, $array){
  if(count($pieces) > 1){
    $key = array_shift($pieces);
    $array[$key] = createArray($pieces, isset($array[$key]) ? $array[$key] : []);
  }
  else{
    $array[$pieces[0]] = [];
  }

  return $array;
}

DEMO: https://eval.in/137546