public function tier($tier)
    {
        return new Plans(array_values(array_filter($this->plans, function ($plan) use ($tier) {
            return $plan->tier === $tier;
        })));
    }
public function tier($tier)
    {
        return new Plans(array_values(array_filter($this->plans, function ($plan) use ($tier) {
            return $plan->tier === $tier;
        })));
    }
public function tier ( $ tier ) { return new Plans ( array_values ( array_filter ( $ this -> plans , function ( $ plan ) use ( $ tier ) { return $ plan -> tier === $ tier ; } ) ) ) ; }
Get all of the monthly plans for a given tier.

@return array
Get all of the monthly plans for a given tier .