How do I access values in a multidimensional array dynamically with a variable number of indices?

Question

Essentially, I have a multidimensional array like this (it's actually much more extensive but this is the bare skeleton I need to access):

$arr = [
    1 => [ 
        'val1' => 'foo',
        'val2' => 'bar',
    ],
    2 => [
        'type1' => [
            'val3' => 'baz',
            'val4' => 'fuz',
        ],
    ],
]

I will be accessing this array dynamically and won't know whether I'll be accessing $arr[1] or $arr[2] until I try to do so. Therefore, I also don't know how many levels deep I need to go until that time comes. I was looking for a function that accesses a varying number of levels deep of a multidimensional array but I can't find anything like that. I know I can do this with an if or switch statement but I'm trying to simplify it as something like:

if ( isset( $arr[$var]...... ) ) {
    return $arr[$var]......;
}

My problem is that I can't figure out how to build a string to replace the "......" with the proper number of indices. I tried making a string using a loop:

function getAccessString( array $arrOfIndices ) {
    $str = '';
    foreach( $arrOfIndices as $index ) {
        $str .= '['.$index.']';
    }
    return $str;
}

However, I couldn't get any variation of that string-making function to work in the sense that I could concatenate it in a way that would access my multidimensional array.

P.S. If there is no way to access this array in a very simple format along the line of this...

if ( isset( $arr[$var]...... ) ) {
    return $arr[$var]......;
}

... I will simply use a switch statement. Using iterators, parsing the array and whatnot are not going to be simpler than the switch statement I've already got.

Look at this: stackoverflow.com/questions/17851340/…

Stijn Bernards
– Stijn Bernards

2014-09-10 20:38:12 +00:00
Commented Sep 10, 2014 at 20:38 — Stijn Bernards
– Stijn Bernards, Commented Sep 10, 2014 at 20:38

Barmar · Accepted Answer · 2014-09-10 20:55:48Z

3

function getArrayElement($arr, $arrayOfIndices) {
    $result = $arr;
    foreach ($arrayOfIndices as $index) {
        $result = $result[$index];
    }
    return $result;
}

$arr = [
    1 => [ 
        'val1' => 'foo',
        'val2' => 'bar',
    ],
    2 => [
        'type1' => [
            'val3' => 'baz',
            'val4' => 'fuz',
        ],
    ],
];
echo getArrayElement($arr, [1, 'val1']); // echoes foo
echo getArrayElement($arr, [2, 'type1', 'val4']); // echoes fuz

edited Sep 10, 2014 at 20:55

answered Sep 10, 2014 at 20:41

Barmar

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1 Comment

Joseph Mills Over a year ago

I don't see how that helps me access a multidimensional array in a simple function...

Jay Blanchard · Accepted Answer · 2014-09-10 21:00:25Z

0

You may want to think about flattening the array using PHP's recursive iterator -

function findValue($needle, $haystack) {
    $iterator = new RecursiveIteratorIterator(new RecursiveArrayIterator($haystack)); 
    foreach($iterator as $key=>$value){
        if($key == $needle) {
            return $value;
        }
    }
}
$result = findValue('val3', $arr);
echo $result; // returns 'baz'

This is setup assuming that you do not have any duplicate keys in your array.

edited Sep 10, 2014 at 21:00

answered Sep 10, 2014 at 20:42

Jay Blanchard

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4 Comments

Barmar Over a year ago

What if there are duplicate keys in different sub-arrays?

Jay Blanchard Over a year ago

It's not perfect for every situation @Barmar, but with a little refactoring it could be made to work. For instance you could push the returned values to an array or you could specify the needle differently.

Barmar Over a year ago

Also seems like an expensive way to do it if the array is big. Every lookup becomes a sequential search instead of an array index.

Jay Blanchard Over a year ago

We're doing some large arrays like this and the expense is not that great but I have not bench-marked those against something like you have done.

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