php中??和?:区别

??和?:区别:

$headerVal = 0;

this->params =this−>params=headerVal ?? 2; 相当于 isset(headerVal) ?headerVal)?headerVal : 2; //结果是0

this->params =this−>params=headerVal ?: 2; 相当于 !empty(headerVal) ?headerVal)?headerVal : 2; //结果是2