我正在用PHP为移动应用程序编写API.端点之一create-user.PHP用于将新记录添加到User表.如果应用程序试图创建副本怎么办？我可以捕获此错误并返回错误消息(顺便说一下,这是？).问题是,我是否还应该返回具有以下结构的JSON：
{
"status": "The email already exists"
}
…向客户提供有关出了什么问题的更多信息？还是我应该只使用错误代码而已？
解决方法:
返回http状态422和错误消息
The 422 (Unprocessable Entity) status code means the server understands the content type of the request entity (hence a 415(Unsupported Media Type) status code is inappropriate), and the Syntax of the request entity is correct (thus a 400 (Bad Request) status code is inappropriate) but was unable to process the contained instructions. For example, this error condition may occur if an XML request body contains well-formed (i.e., syntactically correct), but semantically erroneous, XML instructions.
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具体来说：
422 status code feels much more appropriate. The server understands what you’re trying to do; and it understands the data that you’re submitting; it simply won’t let that data be processed.
从本·纳德尔(Ben Nadel)阅读更多：http://www.bennadel.com/blog/2434-http-status-codes-for-invalid-data-400-vs-422.htm
此外,Laravel框架在“请求表单”类中还使用“失败规则”(例如,电子邮件已经存在)的http状态422.查看此：http://laravel.com/docs/master/validation
