access php array children through parameters?

Question

I have a unique case where I have an array like so:

$a = array('a' => array('b' => array('c' => 'woohoo!')));

I want to access values of the array in a manner like this:

some_function($a, array('a')) which would return the array for position a
some_function($a, array('a', 'b', 'c')) which would return the word 'woohoo'

So basically, it drills down in the array using the passed in variables in the second param and checks for the existence of that key in the result. Any ideas on some native php functions that can help do this? I'm assuming it'll need to make use of recursion. Any thoughts would be really appreciated.

Thanks.

Corey Ballou · Accepted Answer · 2009-12-27 20:52:25Z

2

This is untested but you shouldn't need recursion to handle this case:

function getValueByKey($array, $key) {
    foreach ($key as $val) {
        if (!empty($array[$val])) {
            $array = $array[$val];
        } else return false;
    }
    return $array;
}

answered Dec 27, 2009 at 20:52

Corey Ballou

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1 Comment

onassar Over a year ago

wow, i dunno how you whipped that up so fast, but thanks dude. exactly what i was looking for.

Gordon · Accepted Answer · 2009-12-27 20:51:24Z

2

You could try with RecursiveArrayIterator

Here is an example on how to use it.

answered Dec 27, 2009 at 20:51

Gordon

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1 Comment

onassar Over a year ago

thanks for the tip, but the above one which doesn't use recursion is preferred. much easier to follow :)

Gumbo · Accepted Answer · 2009-12-27 20:56:21Z

2

Here’s a recursive implementation:

function some_function($array, $path) {
    if (!count($path)) {
        return;
    }
    $key = array_shift($path);
    if (!array_key_exists($key, $array)) {
        return;
    }
    if (count($path) > 1) {
        return some_function($array[$key], $path);
    } else {
        return $array[$key];
    }
}

And an iterative implementation:

function some_function($array, $path) {
    if (!count($path)) {
        return;
    }
    $tmp = &$array;
    foreach ($path as $key) {
        if (!array_key_exists($key, $tmp)) {
            return;
        }
        $tmp = &$tmp[$key];
    }
    return $tmp;
}

These functions will return null if the path is not valid.

edited Dec 27, 2009 at 20:56

answered Dec 27, 2009 at 20:51

Gumbo

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3 Comments

onassar Over a year ago

your non-recursive one works about the same way as the chosen one above. thanks though. i appreciate it!

Gumbo Over a year ago

@onassar: But using array_key_exists is more safe since empty returns true for values like "", null, false, array(), 0 and "0".

onassar Over a year ago

true that! thanks sir. i've modified mine to make use of that. i bet that would bit me in the ass way down the line and resulted in hours of debugging :( thanks!

Tatu Ulmanen · Accepted Answer · 2009-12-27 20:50:28Z

1

$a['a'] returns the array at position a.
$a['a']['b']['c'] returns woohoo.

Won't this do?

answered Dec 27, 2009 at 20:50

Tatu Ulmanen

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1 Comment

onassar Over a year ago

couldn't do that as i didn't want to explicitly write access to the value, since it could vary. thanks though!

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