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<?php $a = [ 0 => [ 'price' => 5.5 ], 1 => [ 'price' => 6.0 ], 2 => [ 'price' => 6.2 ], 3 => [ 'price' => 6.5 ], ]; $b = [ 0 => [ 'color' => 'RED' ], 1 => [ 'color' => 'WHITE' ], 2 => [ 'color' => 'BLUE' ], 3 => [ 'color' => 'RED' ], ]; print_r(array_replace_recursive($a, $b));
Output for 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 7.2.6 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 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] => Array ( [price] => 5.5 [color] => RED ) [1] => Array ( [price] => 6 [color] => WHITE ) [2] => Array ( [price] => 6.2 [color] => BLUE ) [3] => Array ( [price] => 6.5 [color] => RED ) )

preferences:
99.64 ms | 1675 KiB | 4 Q