How to use array values as keys without loops?

Question

Looping is time consuming, we all know that. That's exactly something I'm trying to avoid, even though it's on a small scale. Every bit helps. Well, if it's unset of course :)

On to the issue

I've got an array:

array(3) {
    '0' => array(2) {
        'id'   => 1234,
        'name' => 'blablabla',
    },
    '1' => array(2) {
        'id'   => 1235,
        'name' => 'ababkjkj',
    },
    '2' => array(2) {
        'id'   => 1236,
        'name' => 'xyzxyzxyz',
    },
}

What I'm trying to do is to convert this array as follows:

array(3) {
    '1234' => 'blablabla',
    '1235' => 'asdkjrker',
    '1236' => 'xyzxyzxyz',
}

I guess this aint a hard thing to do but my mind is busted right now and I can't think of anything except for looping to get this done.

Answer 1

Simply use array_combine along with the array_column as

array_combine(array_column($array,'id'), array_column($array,'name'));

Or you can simply use array_walk if you have PHP < 5.5 as

$result = array();
array_walk($array, function($v)use(&$result) {
    $result[$v['id']] = $v['name']; 
});

Edited:

For future user who has PHP > 5.5 can simply use array_column as

array_column($array,'name','id');

Fiddle(array_walk)

Answer 2

UPD: Warning the slowest solution! See benchmarks below.

Try this code:

$a = array(array('id'   => 1234,
                 'name' => 'blablabla'),
           array('id'   => 1235,
                 'name' => 'ababkjkj'),
           array('id'   => 1236, 
                 'name' => 'xyzxyzxyz'));

var_export(array_reduce($a, function($res, $item) {
    $res[$item['id']] = $item['name'];
    return $res;
}));

Works fine even in PHP 5.3. And uses only one function array_reduce.

UPD: Here are some benchmarks (PHP 5.6 over Debian 7 on a medium quality server):

$a = [];
for ($i = 0; $i < 150000; $i++) {
    $a[$i] = ['id' => $i,
               'name' => str_shuffle('abcde') . str_shuffle('01234')];
}

$start = microtime(true);

if (false) {
    // 7.7489550113678 secs for 15 000 itmes
    $r = array_reduce($a, function($res, $item) {
             $res[$item['id']] = $item['name'];
             return $res;
         });
}

if (false) {
    // 0.096649885177612 secs for 150 000 items
    $r = array_combine(array_column($a, 'id'),
                       array_column($a, 'name'));
}

if (true) {
    // 0.066264867782593 secs for 150 000 items
    $r = [];
    foreach ($a as $subarray) {
        $r[$subarray['id']] = $subarray['name'];
    }
}

if (false) {
    // 0.32427287101746 secs for 150 000 items
    $r = [];
    array_walk($a, function($v) use (&$r) {
        $r[$v['id']] = $v['name'];
    });
}

echo (microtime(true) - $start)  . ' secs' . PHP_EOL;

So, as a conclusion: plain iteration with simple for loop is a winner (as mentioned in this answer). On a second place there is array_combine allowed only for new versions of PHP. And the worst case is using my own solution with closure and array_reduce.

Answer 3

If you have php >= 5.5:

$res = array_combine(array_column($source, 'id'), array_column($source, 'name'));

If not - make a loop.

Answer 4

Make use of array_map function, (PHP 4 >= 4.0.6, PHP 5)

[akshay@localhost tmp]$ cat test.php
<?php

$array = array(
                array('id'   => 1234,'name' => 'blablabla'),
                array('id'   => 1235,'name' => 'ababkjkj'),
                array('id'   => 1236,'name' => 'xyzxyzxyz')
              );

$output = array();
array_map(function($_) use (&$output){ $output[$_['id']] = $_['name']; },$array);

// Input
print_r($array);

// Output
print_r($output);

?>

Output

[akshay@localhost tmp]$ php test.php
Array
(
    [0] => Array
        (
            [id] => 1234
            [name] => blablabla
        )

    [1] => Array
        (
            [id] => 1235
            [name] => ababkjkj
        )

    [2] => Array
        (
            [id] => 1236
            [name] => xyzxyzxyz
        )

)
Array
(
    [1234] => blablabla
    [1235] => ababkjkj
    [1236] => xyzxyzxyz
)

Answer 5

This is the fastest and simplest code here so far ...

$result = [];
foreach ($input as $subarray) {
    $result[$subarray["id"]] = $subarray["name"];
}

Answer 6

Try this function:

array_combine(array_column($array,'id'), array_column($array,'name'));