Online PHP editor | output for JGDmC

<?php $custom_fields = [ 'foo' => '17', ]; $time_intervals = ['day', 'month', 'year', 'hour', 'minute', 'period']; $data = [ 'fooday' => '17', 'foomonth' => 'March', 'name' => 'Chris' ]; function array_string_multiply($array1, $array2) { foreach ($array1 as $field) { yield array_map(function ($interval) use ($field) { return $field . $interval; }, $array2); } } foreach (array_string_multiply(array_keys($custom_fields), $time_intervals)) as $key) { echo $key . "\n"; } foreach (array_keys($custom_fields) as $name) { foreach ($time_intervals as $interval_name) { // ; } } var_dump($data); // Result should be array that only contains $data['name'] = 'Chris'