framework/db/QueryTrait.php
public function andWhere($condition)
    {
        if ($this->where === null) {
            $this->where = $condition;
        } else {
            $this->where = ['and', $this->where, $condition];
        }

        return $this;
    }
public function andWhere($condition)
    {
        if ($this->where === null) {
            $this->where = $condition;
        } else {
            $this->where = ['and', $this->where, $condition];
        }

        return $this;
    }
Adds an additional WHERE condition to the existing one.
The new condition and the existing one will be joined using the 'AND' operator.
@param string|array|ExpressionInterface $condition the new WHERE condition. Please refer to [[where()]]
on how to specify this parameter.
@return $this the query object itself
@see where()
@see orWhere()