Variable Variables for Array Key - php

Question

Currently I am attempting to call a multidimensional array, using a string as a key or keys. I would like to use the following code, but I think the key is being interpreted as a string. Any solution?
$data= [];
$data['volvo'] = "nice whip";
$test = "['volvo']";
$data['drivers']['mike'] = "decent";
$test2 = "['drivers']['mike']";
echo $data$test; // should read 'nice whip'
echo $data$test2; // should read 'decent'

Answer 1

You just use the variable (which should just be the string and not PHP syntax) in place of the string literal.
$cars = [];
$cars['volvo'] = 'nice whip';
$test = 'volvo';
echo $cars[$test];

Answer 2

If you need a dynamic array access solution, you could also write a function, which does the actual array access like this:
function path($array, $path) {
$path = is_array($path) ? $path : explode('.', $path);
$current = $array;
while (count($path)) {
$seg = array_shift($path);
if (!isset($current[$seg])) throw new Exception('Invalid path segment: ' . $seg);
$current = $current[$seg];
}
return $current;
}
In your case, this would look like this
echo path($data, 'volvo');
echo path($data, 'drivers.mike');
or
echo path($data, ['volvo']);
echo path($data, ['drivers', 'mike']);

Answer 3

The problem is you can't pass multiple levels in one string like that. (If so, PHP would have to start looking for code fragments inside string array keys. And how would it know whether to interpret them as fragments and then split the string key up, or keep treating it as one string??)
Alt 1
One solution is to change the structure of $data, and make it a single level array. Then you supply keys for all the levels needed to find your data, joined together as a string. You would of course need to find a separator that works in your case. If the keys are plain strings then something simple like underscore should work just fine. Also, this wouldn't change the structure of your database, just the way data is stored.
function getDbItem($keys) {
// Use this to get the "old version" of the key back. (I.e it's the same data)
$joinedKey = "['".implode("'],['", $keys)."']";
$joinedKey = implode('_', $keys);
return $data[$joinedKey];
}
// Example
$data = [
'volvo' => 'nice whip',
'drivers_mike' => 'decent'
];
var_dump(getDbItem(['drivers', 'mike'])); // string(6) "decent"
Alt 2
Another way is to not change number of levels in $data, but simply traverse it using the keys passed in:
$tgt = $data;
foreach($keys as $key) {
if (array_key_exists($key, $tgt)) {
$tgt = $tgt[$key];
}
else {
// Non existing key. Handle properly.
}
}
// Example
$keys = ['drivers', 'mike'];
// run the above code
var_dump($tgt); // string(6) "decent"