Access an array variable, with its name stored as string in another array

PHP
1

Hi, please, can you look at my example?

I want to access an array.
The name of this array is stored as string inside another array.
I obtained the name of the array, and done the dump in a successful way as var_dump($$array["array_name"]); look.

But, There is an ERROR when I try to access a particular index as in var_dump($$array["array_name"][1]);.

I don’t know why! Can you help me? Thanks!

<?php
   $foo = array(0 => "string text",
                1 => "another line of string text",
                2 => "etc etc");

   $array = array("array_name" => "foo");

   $array_name = $array["array_name"];



   echo "<p>access directly the array with name 'foo', the row 1</p>";
   var_dump($foo[1]);

   echo "<br><p>access directly the array that contain array variables names</p>";
   var_dump($array["array_name"]);

   echo "<br><p>access indirectly the array that contain array variables names</p>";
   var_dump($$array["array_name"]);

   echo "<br><p>access indirectly the array that contain array variables names, row 1, ERROR!! WHY?</p>";
   var_dump($$array["array_name"][1]);

   echo "<br><p>access indirectly the array that contain array variables names, row 1, ERROR!! WHY?</p>";
   var_dump($$array_name[1]);

?>
3

Ambiguity. Note the curly braces. Though I’m not sure the last one is correct.

echo "<br><p>access indirectly the array that contain array variables names, row 1, ERROR!! WHY?</p>";
var_dump(${$array["array_name"]}[1]);
   
echo "<br><p>access indirectly the array that contain array variables names, row 1, ERROR!! WHY?</p>";
var_dump(${$array_name}[1]);

http://php.net/manual/en/language.variables.variable.php

2 Likes
4

If I am not mistaken, it appears to me that there is no index [1] in $array["array_name"], but rather it appears that $array stores one element at "array_name". Basically $array looks like this:
array=> ["array_name"] => "foo"
You are passing it a string "foo" and not the variable $foo.
Additionally, $array_name doesn’t appear to be an array, so you won’t be able to do var_dump($$array_name[1]); on it, instead it just stores the string "foo"

5

@droopsnoot has resolved the matter. Many thanks!

@fencerman2 $array_name is string that contains the name of the array variable.
So, we can consider $$array_name[1] as:
$$array_name[1]
=${$array_name}[1] =
=${foo}[1] =
= $foo[1]

so, If I understand, the reasoning in my first post was substantially right, but working with arrays produces ambiguity problem that someone can resolve following what droopsnoot said using the curly brackets.

6

Some of those ambiguity problems are resolved one way in PHP 5 and the opposite way in PHP 7 so you should always use {} to remove the ambiguity or the code may break in the future (who knows which way future versions will resolve those ambiguities).

1 Like
7

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