// Created on savesnippets.com · https://savesnippets.com/mEidrqBCBgMiQC
<?php
function indexBy(array $rows, string $key): array {
    $out = [];
    foreach ($rows as $row) {
        if (isset($row[$key])) $out[$row[$key]] = $row;
    }
    return $out;
}

$users = [
    ['id'=>10,'name'=>'Alice'],
    ['id'=>20,'name'=>'Bob'],
];

$byId = indexBy($users, 'id');
echo $byId[20]['name'];   // Bob