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<?php $arX = Array('AAA' => 173.696, 'BBB' => 72.436, 'CCC' => 142.692); $arY = Array('AAA' => 127, 'DDD' => 72.333); $newArray = []; $callback = function($value, $key , $prefix) use (&$newArray) { if (!isset($newArray[$key])) { $newArray[$key] = []; } $newArray[$key] = [$prefix => $value]; }; array_walk($arX , $callback , "X"); array_walk($ary , $callback , "Y"); var_dump($newArray);
Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
Fatal error: Uncaught TypeError: array_walk(): Argument #1 ($array) must be of type array, null given in /in/DKZ3B:18 Stack trace: #0 /in/DKZ3B(18): array_walk(NULL, Object(Closure), 'Y') #1 {main} thrown in /in/DKZ3B on line 18
Process exited with code 255.
Output for 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33
Warning: array_walk() expects parameter 1 to be array, null given in /in/DKZ3B on line 18 array(3) { ["AAA"]=> array(1) { ["X"]=> float(173.696) } ["BBB"]=> array(1) { ["X"]=> float(72.436) } ["CCC"]=> array(1) { ["X"]=> float(142.692) } }

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