core/Field.php
public function __isset($name)
    {
        if ($name[0] == 'b' && preg_match('@^box([A-Z].*)$@', $name, $m)) {
            $name = Utils::camelToAttr($m[1]);
            return isset($this->_attr[$name]);
        } else if ($name[0] == 'd' && preg_match('@^data([A-Z].*)$@', $name)) {
            $name = Utils::camelToAttr($name);
            return isset($this->_data[$name]);
        } else if ($name[0] == 'v' && preg_match('@^view([A-Z].*)$@', $name)) {
            return isset($this->_view[$name]);
        } else if ($name == 'value') {
            return true;
        } else {
            return isset($this->_extends[$name]);
        }
    }
public function __isset($name)
    {
        if ($name[0] == 'b' && preg_match('@^box([A-Z].*)$@', $name, $m)) {
            $name = Utils::camelToAttr($m[1]);
            return isset($this->_attr[$name]);
        } else if ($name[0] == 'd' && preg_match('@^data([A-Z].*)$@', $name)) {
            $name = Utils::camelToAttr($name);
            return isset($this->_data[$name]);
        } else if ($name[0] == 'v' && preg_match('@^view([A-Z].*)$@', $name)) {
            return isset($this->_view[$name]);
        } else if ($name == 'value') {
            return true;
        } else {
            return isset($this->_extends[$name]);
        }
    }
判断属性存在
@param $name
@return bool