如何由多维数组生成键值数组

function flattenArray($array, $prefix = '') {
    $result = array();
    foreach ($array as $key => $value) {
        if (is_array($value)) {
            $result = array_merge($result, flattenArray($value, $prefix . $key . '_'));
        } else {
            $result[$prefix . $key] = $value;
        }
    }
    return $result;
}

// 示例多维数组
$multiDimensionalArray = array(
    'key1' => 'value1',
    'key2' => array(
        'subkey1' => 'subvalue1',
        'subkey2' => 'subvalue2'
    ),
    'key3' => array(
        'subkey3' => array(
            'subsubkey1' => 'subsubvalue1'
        )
    )
);

// 生成键值数组
$keyValueArray = flattenArray($multiDimensionalArray);

// 打印结果
print_r($keyValueArray);