<?php $array = [ "2022-10-30" => ['▶'], "2022-10-31" => ['▶'], "2022-11-07" => ['▶'], "2022-11-09" => ['▶'] ]; $result = []; foreach ($array as $key => $value) { $ym = substr($key, 0, 7); if (!isset($lookup[$ym]) || $lookup[$ym] < $key) { $result[$key] = $value; if (isset($lookup[$ym])) { unset($result[$lookup[$ym]]); } $lookup[$ym] = $key; } } var_export($result);
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