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<?php $numbers = [4, 3, 4, 3, 1, 2, 1]; var_export(array_keys(array_intersect(array_count_values($numbers),[1])));
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 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
array ( 0 => 2, )
preferences:
79.88 ms | 1977 KiB | 4 Q