Converting string to array address - php

Question

I have dynamically generated array $array[], that could be multidimensional and I have a function that return string, which contains address in array (existing one). My question is: how to create or convert string $a = 'array[1]' to address $array[1]?
Example:
$array = [1,2,3,4];
$string = 'array[2]';
function magic($array, $string){
//some magic happens
return $result;
$result = magic($array, $string);
echo $result;
// and 3 is displayed;
Is there a function already to do this? Is it possible to do this?

Answer 1

This code is a modification of ResponseBag::get() from the wonderful HttpFoundation project:
function magic($array, $path, $default = null)
{
if (false === $pos = strpos($path, '[')) {
return $array;
}
$value = $array;
$currentKey = null;
for ($i = $pos, $c = strlen($path); $i < $c; $i++) {
$char = $path[$i];
if ('[' === $char) {
if (null !== $currentKey) {
throw new \InvalidArgumentException(sprintf('Malformed path. Unexpected "[" at position %d.', $i));
}
$currentKey = '';
} elseif (']' === $char) {
if (null === $currentKey) {
throw new \InvalidArgumentException(sprintf('Malformed path. Unexpected "]" at position %d.', $i));
}
if (!is_array($value) || !array_key_exists($currentKey, $value)) {
return $default;
}
$value = $value[$currentKey];
$currentKey = null;
} else {
if (null === $currentKey) {
throw new \InvalidArgumentException(sprintf('Malformed path. Unexpected "%s" at position %d.', $char, $i));
}
$currentKey .= $char;
}
}
if (null !== $currentKey) {
throw new \InvalidArgumentException(sprintf('Malformed path. Path must end with "]".'));
}
return $value;
}
echo magic([1,2,3,4], 'array[2]'); // 3
It can be modified to return a reference as well, just sprinkle it with some ampersands :)