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<?php $array = [ ['city' => 'NewYork', 'cash' => '1000'], ['city' => 'Philadelphia', 'cash' => '2300'], ['city' => 'NewYork', 'cash' => '2000'] ]; foreach ($array as $row) { $result[$row['city']] = [ 'city' => $row['city'], 'cash' => ($result[$row['city']]['cash'] ?? 0) + $row['cash'] ]; } var_export(array_values($result));
Output for 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 - 8.3.31, 8.4.1 - 8.4.22, 8.5.0 - 8.5.7
array ( 0 => array ( 'city' => 'NewYork', 'cash' => 3000, ), 1 => array ( 'city' => 'Philadelphia', 'cash' => 2300, ), )

preferences:
105.44 ms | 1423 KiB | 4 Q