$records = array(
array(
'id' => 21,
'first_name' => 'John',
'last_name' => 'Doe',
),
array(
'id' => 22,
'first_name' => 'Sally',
'last_name' => 'Smith',
),
array(
'id' => 23,
'first_name' => 'Jane',
'last_name' => 'Jones',
),
array(
'id' => 24,
'first_name' => 'Peter',
'last_name' => 'Doe',
)
);
// memecah array
$first_names = array_column($records, 'first_name', 'id');
// echo "<pre>";
// // print_r($first_names);
// print_r(max($first_names));
// // print_r($records);
// echo "</pre>";
// exit();