JSON 字符串和對象對比

$str = '{"extraMap":"{\"app\":\"activitylist.html\"}"}';
var_dump(json_decode($str));

$str1 = '{"extraMap":{"app":"activitylist.html"}}';
var_dump(json_decode($str1));

object(stdClass)#1 (1) {
 ["extraMap"]=>
 string(27) "{"app":"activitylist.html"}"
}
object(stdClass)#2 (1) {
 ["extraMap"]=>
 object(stdClass)#1 (1) {
   ["app"]=>
   string(17) "activitylist.html"
 }
}