3v4l.org

run code in 300+ PHP versions simultaneously
<?php $input = ['a', 'c', 'a', 'b', 'c', 'c']; $count = array_count_values($input); $duplicated = array_keys(array_diff($count, [1])); var_export($duplicated); echo PHP_EOL; echo implode(", ", $duplicated);

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31.43 ms | 408 KiB | 5 Q