Online PHP editor | output for 9rEm4

<?php $years = array( array(2015 => '2015'), array(2016 => '2016'), array(2017 => '2017'), array(2018 => '2018'), array(2019 => '2019'), array(2020 => '2020'), array(2021 => '2021'), array(2022 => '2022'), array(2023 => '2023') ); // var_export(array_merge(...$years)); // loses numeric associative keys // var_export(call_user_func_array('array_merge', $years)); // loses numeric associative keys // var_export(array_reduce($years, 'array_merge', array())); // loses numeric associative keys var_export(iterator_to_array(new RecursiveIteratorIterator(new RecursiveArrayIterator($years))));