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 co

Answer 1

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.