framework/db/BaseActiveRecord.php
public function getAttributeLabel($attribute)
    {
        $labels = $this->attributeLabels();
        if (isset($labels[$attribute])) {
            return $labels[$attribute];
        } elseif (strpos($attribute, '.')) {
            $attributeParts = explode('.', $attribute);
            $neededAttribute = array_pop($attributeParts);

            $relatedModel = $this;
            foreach ($attributeParts as $relationName) {
                if ($relatedModel->isRelationPopulated($relationName) && $relatedModel->$relationName instanceof self) {
                    $relatedModel = $relatedModel->$relationName;
                } else {
                    try {
                        $relation = $relatedModel->getRelation($relationName);
                    } catch (InvalidParamException $e) {
                        return $this->generateAttributeLabel($attribute);
                    }
                    /* @var $modelClass ActiveRecordInterface */
                    $modelClass = $relation->modelClass;
                    $relatedModel = $modelClass::instance();
                }
            }

            $labels = $relatedModel->attributeLabels();
            if (isset($labels[$neededAttribute])) {
                return $labels[$neededAttribute];
            }
        }

        return $this->generateAttributeLabel($attribute);
    }
public function getAttributeLabel($attribute)
    {
        $labels = $this->attributeLabels();
        if (isset($labels[$attribute])) {
            return $labels[$attribute];
        } elseif (strpos($attribute, '.')) {
            $attributeParts = explode('.', $attribute);
            $neededAttribute = array_pop($attributeParts);

            $relatedModel = $this;
            foreach ($attributeParts as $relationName) {
                if ($relatedModel->isRelationPopulated($relationName) && $relatedModel->$relationName instanceof self) {
                    $relatedModel = $relatedModel->$relationName;
                } else {
                    try {
                        $relation = $relatedModel->getRelation($relationName);
                    } catch (InvalidParamException $e) {
                        return $this->generateAttributeLabel($attribute);
                    }
                    /* @var $modelClass ActiveRecordInterface */
                    $modelClass = $relation->modelClass;
                    $relatedModel = $modelClass::instance();
                }
            }

            $labels = $relatedModel->attributeLabels();
            if (isset($labels[$neededAttribute])) {
                return $labels[$neededAttribute];
            }
        }

        return $this->generateAttributeLabel($attribute);
    }
Returns the text label for the specified attribute.
If the attribute looks like `relatedModel.attribute`, then the attribute will be received from the related model.
@param string $attribute the attribute name
@return string the attribute label
@see generateAttributeLabel()
@see attributeLabels()