Unstable reply for WSDL services log_level set to 4

I am testing web services with WSDL model enabled. (I set opparms to "mixed" for functions) with log_level set to 4. While I am calling few functions in a php script called math_service.php, the first request always return a right answer. But the following request is now so stable. Most of time, it return 0 as return. But as soon as I switch to log_level to 0, it works. With log file, I found that deserializations part doesn't work as expected. I have attached my log file (I have modified wsf_wsdl_deserialization.php to add more log lines while debugging) param1, param2 are parameters for addxy function param3, param4 are parameters for add function param5, param6 are parameters for sub function ... I just wonder whether it will cause some problem while there are many calls to same php script at the same time.

Attachment	Size
wsf_php_server.txt	178.87 KB