PHP response true / false and correct IF statemen

In add to cart function can be placed discount, discounts are made via xxx-hashid. i figure out that problem is when user want cheat and type random xxx-123456 my system crash.

hashid is from Ivan Akimov.

is possible to achiev, when hashID (userID) doesnt exist function return code isnt valid but without crash ?

public function getIdByHash($hashid) {
    $response = ['valid' => false];
    if ($hashid){
        $response['valid'] = true;
        $hashid = explode("PMX-",$hashid)[1];
        $hashids = new Hashids("",6);  
    return $hashids->decode($hashid)[0];
    } 
        if ($hashid){
            $response ['valid'] = false;
        return $hashids = "PMX-"."dGRLrb";
        }
    }