How to convert an array of arrays or objects to an associative array?

I had the exact same problem some days ago. It is not possible using array_map, but array_reduce does the trick.

$arr = array('a','b','c','d');
$assoc_arr = array_reduce($arr, function ($result, $item) {
    $result[$item] = (($item == 'a') || ($item == 'c')) ? 'yes' : 'no';
    return $result;
}, array());


array(4) { ["a"]=> string(3) "yes" ["b"]=> string(2) "no" ["c"]=> string(3) "yes" ["d"]=> string(2) "no" }

As far as I know, it is completely impossible in one expression, so you may as well use a foreach loop, à la

$new_hash = array();

foreach($original_array as $item) {
    $new_hash[$item] = 'something';

If you need it in one expression, go ahead and make a function:

function array_map_keys($callback, $array) {
    $result = array();

    foreach($array as $item) {
        $r = $callback($item);

        $result[$r[0]] = $r[1];

    return $result;

This is a clarification on my comment in the accepted method. Hopefully easier to read. This is from a WordPress class, thus the $wpdb reference to write data:

class SLPlus_Locations {
    private $dbFields = array('name','address','city');

    public function MakePersistent() {
        global $wpdb;
        $dataArray = array_reduce($this->dbFields,array($this,'mapPropertyToField'));

    private function mapPropertyToField($result,$property) {
        $result[$property] = $this->$property;
        return $result;

Obviously there is a bit more to the complete solution, but the parts relevant to array_reduce() are present. Easier to read and more elegant than a foreach or forcing the issue through array_map() plus a custom insert statement.




Array Map