为什么环信服务器返回的json结果解析后内容添加了其他东西

s:482:"{
"action" : "post",
"application" : "64cdce70-e829-11e4-b003-97805bb922ee",
"path" : "/users",
"uri" : "https://a1.easemob.com/415426507/test/users",
"entities" : ,
"timestamp" : 1429878307775,
"duration" : 25,
"organization" : "415426507",
"applicationName" : "test"
}";

s:482:这个是什么东西来的？为什么会多出这个东西