src/Neutrino/Support/Arr.php
public static function add($array, $key, $value)
    {
        if (is_null(self::get($array, $key))) {
            self::set($array, $key, $value);
        }

        return $array;
    }
public static function add($array, $key, $value)
    {
        if (is_null(self::get($array, $key))) {
            self::set($array, $key, $value);
        }

        return $array;
    }
Add an element to an array using "dot" notation if it doesn't exist.

@param array  $array
@param string $key
@param mixed  $value

@return array