use strings to access (potentially large) multidimensional arrays - php

Question

I am having trouble figuring out a way to simply parse a string input and find the correct location within a multidimensional array.
I am hoping for one or two lines to do this, as the solutions I have seen rely on long (10-20 line) loops.
Given the following code (note that the nesting could, in theory, be of any arbitrary depth):
function get($string)
{
$vars = array(
'one' => array(
'one-one' => "hello",
'one-two' => "goodbye"
),
'two' => array(
'two-one' => "foo",
'two-two' => "bar"
)
);
return $vars[$string]; //this syntax isn't required, just here to give an idea
}
get("two['two-two']"); //desired output: "bar". Actual output: null
Is there a simple use of built-in functions or something else easy that would recreate my desired output?

Answer 1

Considering $vars being your variables you would like to get one['one-one'] or two['two-two']['more'] from (Demo):
$vars = function($str) use ($vars)
{
$c = function($v, $w) {return $w ? $v[$w] : $v;};
return array_reduce(preg_split('~\[\'|\'\]~', $str), $c, $vars);
};
echo $vars("one['one-one']"); # hello
echo $vars("two['two-two']['more']"); # tea-time!
This is lexing the string into key tokens and then traverse the $vars array on the keyed values while the $vars array has been turned into a function.
Older Stuff:
Overload the array with a function that just eval's:
$vars = array(
'one' => array(
'one-one' => "hello",
'one-two' => "goodbye"
),
'two' => array(
'two-one' => "foo",
'two-two' => "bar"
)
);
$vars = function($str) use ($vars)
{
return eval('return $vars'.$str.';');
};
echo $vars("['one']['one-two']"); # goodbye
If you're not a fan of eval, change the implementation:
$vars = function($str) use ($vars)
{
$r = preg_match_all('~\[\'([a-z-]+)\']~', $str, $keys);
$var = $vars;
foreach($keys[1] as $key)
$var = $var[$key];
return $var;
};
echo $vars("['one']['one-two']"); # goodbye

Answer 2

How about
$vars = array(
'one' => array(
'one-one' => "hello",
'one-two' => "goodbye"
),
'two' => array(
'two-one' => "foo",
'two-two' => "bar"
)
);
function get( $string, $vars )
{
$keys = explode( '][', substr( $string, 1, -1 ) );
foreach( $keys as $key ) {
$vars = $vars[$key];
}
return $vars;
}
echo get( '[two][two-one]', $vars );

Answer 3

For one, you've not got a $var in your get() function. $var was defined outside the function, and PHP scoping rules do not make "higher" vars visible in lower scopes unless explictly made global in the lower scope:
function get($string) {
global $vars;
eval('$x = $vars' . $string);
return $x;
}
get("['two']['two-two']");
might work, but this isn't tested, and using eval is almost always a very bad idea.

Answer 4

Kohana has a nice Config class which alows something like this:
echo Config::get("two.two-two");
You can check it out here: http://kohanaframework.org/3.1/guide/api/Config