How to get key or index name from value in array without iteration?

Question

I have a two dimensional array. I'm trying to get the key/index name of a given value. How do I do this? I went through the PHP manual and they suggest to do an iteration, but I do not want to iterate. Is there a way to do without iteration?

I would like to do something similar to

$country = 'Algeria';
echo $iso_countries[$country]; //obviously this will throw an error since the index does not exist. It's just an example.

array

$iso_countries = array
(
    'AF' => 'Afghanistan',
    'AX' => 'Aland Islands',
    'AL' => 'Albania',
    'DZ' => 'Algeria',
);

If the array is sorted by value you can do a binary search which will find any entry in a list of 256 or fewer entries in at most 8 steps. Other than that, you'd need to pre-build an index that maps country names to their abbreviations, which is essentially what array_flip() will do. — Sammitch
– Sammitch, Commented Apr 28, 2020 at 1:17
You should also disabuse yourself of the notion that "loops are bad". Loops are fundamental to doing virtually everything and you should instead invest your effort in learning when/why loops can be used badly and avoid those, rather than trying to engineer around a non-existent problem. — Sammitch
– Sammitch, Commented Apr 28, 2020 at 1:23

Antonio Abrantes · Accepted Answer · 2020-04-28 01:26:26Z

2

You should use array_search

$iso_countries = array
(
    'AF' => 'Afghanistan',
    'AX' => 'Aland Islands',
    'AL' => 'Albania',
    'DZ' => 'Algeria',
);

$founded = array_search('Algeria',$iso_countries);
echo $founded;

answered Apr 28, 2020 at 1:26

Antonio Abrantes

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LF-DevJourney · Accepted Answer · 2020-04-28 02:08:46Z

No there is no way to get the key of value from an array without an explicit (foreach,while,for) or implicit (in_array,array_flip,array_search) iteration.

PHP ARRAY MANUAL: An array in PHP is actually an ordered map. A map is a type that associates values to keys. This type is optimized for several different uses; it can be treated as an array, list (vector), hash table (an implementation of a map), dictionary, collection, stack, queue, and probably more. As array values can be other arrays, trees and multidimensional arrays are also possible.

From the doc, array is a map which is used to get the value from the index or key, not the contrary.

If you do many search with $country,you can flip the $iso_contries then use index to get the value.

$iso_countries = array
(
    'AF' => 'Afghanistan',
    'AX' => 'Aland Islands',
    'AL' => 'Albania',
    'DZ' => 'Algeria',
);
$iso_countries = array_flip($iso_countries);
$country = 'Algeria';
echo $iso_countries[$country];

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