Thank you for your tips, Waitman.
2>&1 actually works. I was wrong on my test. Exec function successfully catches the output.
The error message was:
"command" is not recognized as an internal or external command, operable program or batch file
file name, directory name or volume label syntax is incorrect
The message was Japanese in reality, but a short Google search shows the message was as the above in English.
What I have found out in the further tests, the problem lies in space characters in the parameter.
I had added " (double quote) in the beginning of the parameter and in its end. But this does not work well.
When I do not add "(double quote), as a matter of course, if the parameter includes space character, this does not work.
I thought the application (abc.exe) has a bug in dealing with a double quote within the parameter, but the same program works in Windows local server (Xampp).
On PHPexe, however, the same program does not work. So I wonder why.
Thank you in advance.
2018年1月14日日曜日 1時45分33秒 UTC+9 Waitman Gobble: