yii\db\QueryBuilder::buildInCondition PHP Method

    public function buildInCondition($operator, $operands, &$params)
    {
        if (!isset($operands[0], $operands[1])) {
            throw new Exception("Operator '{$operator}' requires two operands.");
        }
        list($column, $values) = $operands;
        if ($column === []) {
            // no columns to test against
            return $operator === 'IN' ? '0=1' : '';
        }
        if ($values instanceof Query) {
            return $this->buildSubqueryInCondition($operator, $column, $values, $params);
        }
        if (!is_array($values) && !$values instanceof \Traversable) {
            // ensure values is an array
            $values = (array) $values;
        }
        if ($column instanceof \Traversable || count($column) > 1) {
            return $this->buildCompositeInCondition($operator, $column, $values, $params);
        } elseif (is_array($column)) {
            $column = reset($column);
        }
        $sqlValues = [];
        foreach ($values as $i => $value) {
            if (is_array($value) || $value instanceof \ArrayAccess) {
                $value = isset($value[$column]) ? $value[$column] : null;
            }
            if ($value === null) {
                $sqlValues[$i] = 'NULL';
            } elseif ($value instanceof Expression) {
                $sqlValues[$i] = $value->expression;
                foreach ($value->params as $n => $v) {
                    $params[$n] = $v;
                }
            } else {
                $phName = self::PARAM_PREFIX . count($params);
                $params[$phName] = $value;
                $sqlValues[$i] = $phName;
            }
        }
        if (empty($sqlValues)) {
            return $operator === 'IN' ? '0=1' : '';
        }
        if (strpos($column, '(') === false) {
            $column = $this->db->quoteColumnName($column);
        }
        if (count($sqlValues) > 1) {
            return "{$column} {$operator} (" . implode(', ', $sqlValues) . ')';
        } else {
            $operator = $operator === 'IN' ? '=' : '<>';
            return $column . $operator . reset($sqlValues);
        }
    }