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<?php $array = [ 'Foo', 'bAr', 'BaR', 'fOO', 'baR', ]; $result = []; foreach ($array as $v) { $result[mb_strtoupper($v)] ??= $v; } var_export(array_values($result));
Output for 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 => 'Foo', 1 => 'bAr', )

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