public class oppTrigClass {
    public class oppRecord {
        public string oppId {get;set;}
        public string ownerId{get;set;}
        public date cDate{get;set;}
        public string stage{get;set;}
    }
    //
    @future(callout = true)
    public static void postOppInfo(list<Id> oppIds){
        //Create JSON generator
        JSONGenerator gen = JSON.createGenerator(true);
        gen.writeStartArray();
            for(Id oppId : oppIds){
                gen.writeStartObject();
                gen.writeStringField('Opportunity id', oppId);
                gen.writeStringField('Stage', oppId.StageName);
                //gen.writeStringField('owner id', oppId.ownerId);
                //gen.writeDateField('close date', oppId.cDate);
                gen.writeEndObject();
            }
        gen.writeEndArray();
        string jsonOpps = gen.getAsString();
        system.debug('Opportunities:' + jsonOpps);
    }
}