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<?php $arrays = [ ['car' => '3', 'bus' => '2'], ['dog' => '1', 'car' => '2', 'bird' => '9'], ]; $defaults = array_fill(0, count($arrays), null); $result = []; foreach ($arrays as $i => $array) { foreach ($array as $k => $v){ $result[$k] ??= $defaults; $result[$k][$i] = $v; } } var_export($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 ( 'car' => array ( 0 => '3', 1 => '2', ), 'bus' => array ( 0 => '2', 1 => NULL, ), 'dog' => array ( 0 => NULL, 1 => '1', ), 'bird' => array ( 0 => NULL, 1 => '9', ), )

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