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<?php $array = [ [ 'wd[wd5][amount]' => 1.00, 'wd[wd5][address]' => '1BitcoinAddress', 'wd[wd5][currency]' => 'BTC', ], [ 'wd[wd7][amount]' => 1.00, 'wd[wd7][address]' => '1BitcoinAddress', 'wd[wd7][currency]' => 'BTC' ], ]; $result = []; foreach(new RecursiveIteratorIterator( new RecursiveArrayIterator($array) ) as $key => $value) { $result[$key] = $value; } print_r($result);
Output for 7.0.0 - 7.0.24, 7.1.0 - 7.1.20, 7.2.6 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.26, 8.4.1 - 8.4.13
Array ( [wd[wd5][amount]] => 1 [wd[wd5][address]] => 1BitcoinAddress [wd[wd5][currency]] => BTC [wd[wd7][amount]] => 1 [wd[wd7][address]] => 1BitcoinAddress [wd[wd7][currency]] => BTC )

preferences:
142.24 ms | 408 KiB | 5 Q