3v4l.org

run code in 500+ 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);
Output for 7.1.25 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.31, 8.4.1 - 8.4.22, 8.5.0 - 8.5.7
array ( 0 => 'a', 1 => 'c', ) a, c
preferences:
109.69 ms | 1512 KiB | 4 Q