scanimage和shell_exec ......可能吗？

I have a problem with a script :

When I try to do shell_exec("scanimage > /var/www/html/site/scans") nothing happens. But if I just do echo shell_exec("scanimage -L"), it returns the good result. User www-data is well in the scanner group.

I don't understand anything !! Please help me.

EDIT : I solved the solution by usermod -aG www-data lp, then reboot.

Try using the backtick operator:

`scanimage > /var/www/html/site/scans`;