3v4l.org

run code in 300+ PHP versions simultaneously
<?php $unique = ''; foreach (array_count_values(str_split('abclkjabc')) as $char => $count) { if ($count === 1) { $unique .= $char; } } echo $unique;
Output for 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 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
lkj

preferences:
98.06 ms | 1478 KiB | 4 Q