deep_hash.rb

deep_symbolize_keys = lambda do |hash|  
  return hash unless hash.is_a?(Hash)

  Hash[ hash.map do |key, value|
    # if value is array, loop each element and recursively symbolize keys
    if value.is_a? Array
      value = value.map { |element| symbolize_keys.call(element) }
    # if value is hash, recursively symbolize keys
    elsif value.is_a? Hash
      value = symbolize_keys.call(value)
    end

    [key.to_sym, value]
  end ]
end

deep_symbolize_keys.call(params)