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<?php function array_flatten($array, $result = []) { if(!is_array($array)) { return false; } foreach($array as $key => $value) { if(is_array($value)) { $result = array_flatten($value, $result); } else { $result[$key] = $value; } } return $result; } $allowedKeys = [ 'firstname', 'middlename', 'street', 'lastname', 'housenumber', ]; $userdata = [ 'firstname' => 'first', 'middlename' => 'middle', 'lastname' => 'last', 'address' => [ 'street' => 'streeeeeet', 'housenumber' => '10' ] ]; $addresses = array_flatten($userdata); foreach($userdata as $key => $value) { if(!in_array($key, $allowedKeys)) { unset($userdata[$key]); } } var_dump($addresses);
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 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 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
array(5) { ["firstname"]=> string(5) "first" ["middlename"]=> string(6) "middle" ["lastname"]=> string(4) "last" ["street"]=> string(10) "streeeeeet" ["housenumber"]=> string(2) "10" }

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