Unique request identifier.
Parses the request string as if req=img were specified, but without substituting variables and evaluating referenced objects (images, ICC profiles, fonts, and so forth). The standard error response is returned if parsing fails, otherwise the following property is returned:
The HTTP response is not cacheable.
Requests that support JSONP response format lets you specify the name of the JS callback handler using the extended syntax of req= parameter:
req=...,json [&handler = reqHandler ]
<reqHandler> is the name of the JS handler that is present in the JSONP response. Only a-z, A-Z, and 0-9 characters are allowed. Optional. Default is s7jsonResponse .