php exec（）函数不适用于ubuntu + nginx + fpm上的所有命令

I can see the result of:

echo exec("whoami"); // will output "www-data"

however if I try to run a real world command:

echo exec("casperjs myscript.js /foo/bar");

then nothing happens:

• no output (the casperjs script should output some stdout log messages)
• no action (the script should create an image, using an absolute path, but it doesn't)
• no errors from PHP
• no output of the shell command

I've searched on StackOverflow, and went to try alternative ways (tested first in the shell, to be sure they work):

echo exec("casperjs /absolute/path/to/myscript.js");
echo exec("/usr/local/bin/casperjs /absolute/path/to/myscript.js");

I tested also other combinations, using system(), shell_exec() and even passthru() but it's always the same thing: no error, no output, even in php log files, so it is very, very hard to understand the problem :(

Try echo exec("casperjs myscript.js /foo/bar 2>&1"); to redirect stderr to stdout which wouldn't otherwise show.

It could be an error in your cmdline or maybe casperjs is not in your $PATH, etc.