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<?php $a = ['a' => [1,2,3], 'b' => [4,5,6], 'c' => [7,8,9]]; var_dump( array_slice($a, 0, 2) + ['xxx' => [10,11,12]] + array_slice($a, 2, count($a) - 2) );

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45.62 ms | 402 KiB | 5 Q