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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 - 8.1.31, 8.2.0 - 8.2.26, 8.3.0 - 8.3.14, 8.4.1
lkj

preferences:
59.11 ms | 406 KiB | 5 Q