Illuminate\Database\Query\Builder::whereIn PHP Method

    public function whereIn($column, $values, $boolean = 'and', $not = false)
    {
        $type = $not ? 'NotIn' : 'In';
        if ($values instanceof static) {
            return $this->whereInExistingQuery($column, $values, $boolean, $not);
        }
        // If the value of the where in clause is actually a Closure, we will assume that
        // the developer is using a full sub-select for this "in" statement, and will
        // execute those Closures, then we can re-construct the entire sub-selects.
        if ($values instanceof Closure) {
            return $this->whereInSub($column, $values, $boolean, $not);
        }
        if ($values instanceof Arrayable) {
            $values = $values->toArray();
        }
        $this->wheres[] = compact('type', 'column', 'values', 'boolean');
        foreach ($values as $value) {
            if (!$value instanceof Expression) {
                $this->addBinding($value, 'where');
            }
        }
        return $this;
    }

 /**
  * @param QueryBuilder $builder
  * @param $data
  *
  * @return void
  */
 public function applyFilterConstraint(QueryBuilder $builder, $data)
 {
     if (empty($data)) {
         return;
     }
     $builder->whereIn($this->relation->getForeignKey(), explode(',', $data));
 }