CODEWITHSUNDEEP
phparraysreplacemappinglookup
Josh Petitt
Josh Petitt

Reputation: 9579

Replace values in a flat array using an associative, lookup/mapping array

This should be an easy one liner, but I can't quite get it:

I have an array like this:

$a = ["z", "x", "y"];

and an array like this:

$b = ["x"=>"a", "y"=>"b", "z"=>"c"];

what is a php oneliner to get:

$c = ["c", "a", "b"];

I want to use each element of a to index into b and return an array of the results I've been looking at array_map but couldn't figure out how to bind b to the callback function.

Upvotes: 2

Views: 7609

Answers (4)

mickmackusa
mickmackusa

Reputation: 47854

With modern PHP, you can use arrow function syntax to access the second array without use(). As you iterate all of the values in the first array, check the mapping/second array for a matching key. If a match is found, use that; otherwise use the null coalescing operator to fallback to the original value.

Code: (Demo)

var_export(
    array_map(
        fn($v) => $b[$v] ?? $v,
        $a
    )
);

With the asker's original arrays, all elements are mapped, so the null coalescing is not necessary -- this is just a way to cover similar questions with missing keys in the lookup array.

If the lookup array might contain null values, then you'll need to use key_exists() like this.

Upvotes: 1

TFennis
TFennis

Reputation: 1423

$c = array();
foreach ($a as $key => $value)
{
    if (isset($b[$value]))
    {
       $c[] = $b[$value];
    }
}

Upvotes: 2

Josh Petitt
Josh Petitt

Reputation: 9579

Here is the solution I ended up with with help from @onetrickpony:

$a = array("z", "x", "y");
$b = array("x"=>"a", "y"=>"b", "z"=>"c");

$c = array_map(function($key) use ($b){ return $b[$key]; }, $a);

The key to this is the 'use' keyword to bind to the associative array to the closure. Pretty simple once you know what you are looking for :-)

Upvotes: 1

nice ass
nice ass

Reputation: 16709

$c = array_merge(array_intersect_key(array_flip($a), $b), $b);
$c = array_values($c);

Not really a one-liner, but close :P

Upvotes: 2

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