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run code in 300+ PHP versions simultaneously
<?php $in = [ [ 'id' => 352, 'name' => 'a' ], [ 'id' => 438, 'name' => 'b' ], [ 'id' => 351, 'name' => 'c' ], ]; $out = array_map(function ($arr) { $arr['selected'] = null; return $arr; }, $in); print_r($out);
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.7
Array ( [0] => Array ( [id] => 352 [name] => a [selected] => ) [1] => Array ( [id] => 438 [name] => b [selected] => ) [2] => Array ( [id] => 351 [name] => c [selected] => ) )

preferences:
171.05 ms | 404 KiB | 302 Q