$users = [
[
"id" => '1234567',
"fname" => 'Tim',
],
[
"id" => '9876563',
"fname" => 'Ben',
],
[
"id" => '3805732',
"fname" => 'Selena',
],
[
"id" => '4563524',
"fname" => 'Fei',
]
];
$ids = array_column($users, 'id', 'id');
if (isset($ids[4563524]))
echo "key exist";
/*
run:
key exist
*/