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<?php $a1 = ['a', 'b', null, 'd']; $a2 = ['a', 'b', 'c', 'd']; $filtered1 = array_diff($a1, array_filter($a1)); print_r($filtered1); $filtered2 = array_diff($a2, array_filter($a2)); print_r($filtered2);
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 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.26, 8.4.1 - 8.4.13
Array ( [2] => ) Array ( )

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