Online PHP editor | output for 5KZIi

<?php $array = [ 1650 => ["firstName" => "jack", "lastName" => "straw"], 1649 => ["firstName" => "jack", "lastName" => "straw"], 1651 => ["firstName" => "jack", "lastName" => "straw"], 1652 => ["firstName" => "jack", "lastName" => "straw"], 1653 => ["firstName" => "jack1", "lastName" => "straw"], 1654 => ["firstName" => "jack1", "lastName" => "straw"] ]; ksort($array); $temp = []; foreach ($array as $key => $row) { $compositeKey = $row['firstName'] . '-' . $row['firstName']; $temp[$compositeKey] ??= $row; $temp[$compositeKey]['mergedWith'][] = $key; } $result = []; foreach ($temp as $row) { $result[array_shift($row['mergedWith'])] = $row; } var_export($result);