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<?php $input_array = [ ['id' => 2, 'name' => 'ProductName', 'comment' => 'best product comment 1'], ['id' => 2, 'name' => 'ProductName', 'comment' => 'best product comment 2'], ['id' => 2, 'name' => 'ProductName', 'comment' => 'best product comment 3'], ['id' => 3, 'name' => 'ProductName2', 'comment' => 'best product comment 4'], ['id' => 3, 'name' => 'ProductName2', 'comment' => 'best product comment 5'] ]; $output_array = array_values(array_reduce($input_array, function($output_array, $item) { if (array_key_exists($item['id'], $output_array)) $output_array[$item['id']]['comment'][] = $item['comment']; else { $item['comment'] = (array)$item['comment']; $output_array[$item['id']] = $item; } return $output_array; }, [])); var_dump($output_array);
Output for 5.6.38, 7.1.0 - 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 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.4, 8.3.6 - 8.3.7
array(2) { [0]=> array(3) { ["id"]=> int(2) ["name"]=> string(11) "ProductName" ["comment"]=> array(3) { [0]=> string(22) "best product comment 1" [1]=> string(22) "best product comment 2" [2]=> string(22) "best product comment 3" } } [1]=> array(3) { ["id"]=> int(3) ["name"]=> string(12) "ProductName2" ["comment"]=> array(2) { [0]=> string(22) "best product comment 4" [1]=> string(22) "best product comment 5" } } }
Output for 8.3.5
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0 array(2) { [0]=> array(3) { ["id"]=> int(2) ["name"]=> string(11) "ProductName" ["comment"]=> array(3) { [0]=> string(22) "best product comment 1" [1]=> string(22) "best product comment 2" [2]=> string(22) "best product comment 3" } } [1]=> array(3) { ["id"]=> int(3) ["name"]=> string(12) "ProductName2" ["comment"]=> array(2) { [0]=> string(22) "best product comment 4" [1]=> string(22) "best product comment 5" } } }

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