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<?php $a = Array ( '0' => Array ( 'id' => 1, 'color' => 'red' ), '1' => Array ( '0' => Array ( 'id' => 2, 'color' => 'blue' ), '1' => Array ( '0' => Array ( 'id' => 3, 'color' => 'green' ) ), '2' => Array ( 'id' => 4, 'color' => 'blue' ) ), '2' => Array ( 'id' => 5, 'color' => 'purple' ) ); $i = 0; array_walk_recursive($a, function($v,$k)use(&$r,&$i){ $r[$i][$k] = $v; ($k == 'color') ? $i++ :$i; }); echo '<pre>'; print_r($r);
Output for 7.1.25 - 7.1.33, 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 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
<pre>Array ( [0] => Array ( [id] => 1 [color] => red ) [1] => Array ( [id] => 2 [color] => blue ) [2] => Array ( [id] => 3 [color] => green ) [3] => Array ( [id] => 4 [color] => blue ) [4] => Array ( [id] => 5 [color] => purple ) )

preferences:
93.73 ms | 1591 KiB | 4 Q