Scheduled task execution php file problems

A. php file, and write a bat, the content is: C: \ wamp \ bin \ php \ php5.3.8 \ php.exe-fE: \ photoselect \ work \. php regularly executes bat in the task plan. if it is set to execute once every 5 minutes, but usually 5 minutes is not enough, it will run another bat five minutes later.
I wrote a. php file,
I wrote another bat with the following content:
C: \ wamp \ bin \ php \ php5.3.8 \ php.exe-f E: \ photoselect \ work \ a. php

Execute bat in a scheduled task and set it to be executed once every 5 minutes.

However, it often fails to be processed in five minutes. after five minutes, another bat task will be run, which may cause an error,
(The task has not been completed when it has been set in the scheduled task, but the new instance does not exist .)

Thank you for your help.

------ Solution --------------------
After five minutes, you can only find a way to improve efficiency of a. php. check the bottleneck and consider multithreading.


In addition, you cannot afford to launch new instances. it is for bat. in php, you need to implement duplicate process detection on your own.
------ Solution --------------------
Modify the file running in a. php to determine whether the file is still running. If yes, exit directly. If no, the destroy mark is terminated.