framework/db/BaseActiveRecord.php
public function isAttributeChanged($name, $identical = true)
    {
        if (isset($this->_attributes[$name], $this->_oldAttributes[$name])) {
            if ($identical) {
                return $this->_attributes[$name] !== $this->_oldAttributes[$name];
            }

            return $this->_attributes[$name] != $this->_oldAttributes[$name];
        }

        return isset($this->_attributes[$name]) || isset($this->_oldAttributes[$name]);
    }
public function isAttributeChanged($name, $identical = true)
    {
        if (isset($this->_attributes[$name], $this->_oldAttributes[$name])) {
            if ($identical) {
                return $this->_attributes[$name] !== $this->_oldAttributes[$name];
            }

            return $this->_attributes[$name] != $this->_oldAttributes[$name];
        }

        return isset($this->_attributes[$name]) || isset($this->_oldAttributes[$name]);
    }
Returns a value indicating whether the named attribute has been changed.
@param string $name the name of the attribute.
@param bool $identical whether the comparison of new and old value is made for
identical values using `===`, defaults to `true`. Otherwise `==` is used for comparison.
This parameter is available since version 2.0.4.
@return bool whether the attribute has been changed