3v4l.org

run code in 300+ PHP versions simultaneously
<?php $first = Array(607,608,609,610); $second = Array(607,608,609,800); $Fcount = count($first); $arr = array_merge($first, $second); $arrc= key(array_diff($arr, array_diff_assoc($arr, array_unique($arr)))); echo $arrc;

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47.42 ms | 402 KiB | 5 Q