Array lookup value from dynamic string - php

Question

I'm trying to build a dynamic associative array value lookup function (within a class):
class Family
{
public static $members = array(
'one' => array(
'child' => 0,
'children' => 5
),
'two' => array(
'child' => 2,
'children' => null
)
);
public static function resolveMemberValue()
{
$chain = func_get_args();
$lookup = 'members' . '[\'' . implode('\'][\'', $chain) . '\']';
var_dump( $lookup );
return static::$$lookup;
}
}
Family::resolveMemberValue('one', 'child');
But this results in:
string(23) "members['one']['child']"
Fatal error: Access to undeclared static property: Family::$members['one']['child'] in /family.php on line 23
PHP Fatal error: Access to undeclared static property: Family::$members['one']['child'] in /family.php on line 23
Though, copying the dumped value, and pasting inside the script + appending dollar sign, it returns what's expected:
var_dump( Family::$members['one']['child'] );
int(0)
Reason why I need this is, because it will be used with multiple variables, and called from generator functions.
What is wrong with the snippet?

Answer 1

Variable variables only substitutes in a string for the name of the variable. It can't evaluate the content of that string (in this case the string members['one']['child'])
Your code is looking for a static property literally with the named $members['one']['child'] not an element of the static array $members.
Try this instead:
$member = static::$members[$chain[0]];
return $member[$chain[1]];
Also, I'd recommend not using func_get_args(), but explicitly naming your parameters in the method declaration. Some features of PHP a best left behind....

Answer 2

Oh, had to just tinker a little - managed to make a helper function.
The function replaces the implode() and the explicit key definition.
function array_lookup()
{
$chain = func_get_args();
$array = array_shift($chain);
foreach ($chain as $key) $array = $array[$key];
return $array;
}
$test = array(
'one' => array(
'child' => 0,
'children' => 5
),
'two' => array(
'child' => 2,
'children' => null
)
);
var_dump($test, 'one', 'child'); // int(0)
I have left out any kind of error checking for this example, but it does what I was looking for.
And yes, for my example, it nails it.