Cocoa error 3840

Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (JSON text did not start with array or object and option to allow fragments not set.) UserInfo=0x7fb73347bcf0 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set., NSUnderlyingError=0x7fb7337b3820 "Request failed: internal server error (500)"}

后台PHP的问题 ，找后台处理 ，后台PHP请求返回信息的代码有问题 ，特殊字符之类的。