Declare a multidimensional array by using the values of a flat array as the keypath to a pre-defined value

I have array like this: $test = array(20, 30, 40);

And I want to set a multi-dimension array with using these values: $example[20][30][40] = 'string'

How can I do this?

Note: "20, 30, 40" just an example, my program will print some integers, and I want to set a multi-dimension array with these values and it can be more than 3 values.

You could do it that way:

$example[$test[0]][$test[1]][$test[2]] = 'string'

Or if the size of the array is variable you will need to do a recursive function to fill up your array.

function fill_up($content, $value){
    $index = array_shift($content);
    if(count($content)){
        return array($index => fill_up($content, $value));
    } else {
        return array($index => $value);
    }
}

$example = array(20,30,40);
$value = 'test';
var_dump(fill_up($example, $value));