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<?php function array_not_unique(array $a): array { return array_diff_key( $a, array_unique($a) ); } $array = [ 'apple', 'orange', 'pear', 'banana', 'apple', 'pear', 'kiwi', 'kiwi', 'kiwi' ]; var_export(array_not_unique($array));
Output for 7.4.5, 8.0.1 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.7
array ( 4 => 'apple', 5 => 'pear', 7 => 'kiwi', 8 => 'kiwi', )
preferences:
74.62 ms | 402 KiB | 92 Q