Question

Everybody knows that you can access a variable in PHP using this: ${‘varName’}. But when you need to get/set a variable witch is part of an array, why doesn’t it work ? Suppose we have this piece of code:

<?php
   $myArray = array(...);
   $myVarName = "myArray['my1']['my11']['my111']";
   ${$myVarName} = "new value";
?>

Shouldn’t it work ?
I have tested it again and again – it is not working..
Is it there a way to do that?

Answer 1

I recommend you not to use dynamic variables like ${$var}.
What you want is modifying a multi-dimensional associative array according to a path of keys.

<?php
$myArray = array(...); // multi-dimensional array
$myVarPath = array('my1', 'my11', 'my111');
setValueFromPath($myArray, $myVarPath);

function getValueFromPath($arr, $path)
{
    // todo: add checks on $path
    $dest = $arr;
    $finalKey = array_pop($path);
    foreach ($path as $key) {
        $dest = $dest[$key];
    }
    return $dest[$finalKey];
}

function setValueFromPath(&$arr, $path, $value)
{
    // we need references as we will modify the first parameter
    $dest = &$arr;
    $finalKey = array_pop($path);
    foreach ($path as $key) {
        $dest = &$dest[$key];
    }
    $dest[$finalKey] = $value;
}

This is a procedural example to keep it simple. You may want to put your hierarchical array and this functions inside a class.