phantomJS在通过PHP执行时不起作用

i have installed on my server phantomJS (to /usr/bin/phantomjs) when i run it from the shell as root it works perfectly fine, but when i try to run it via PHP it does not work, those are the commands i have tried:

exec('/usr/bin/phantomjs --version');
shell_exec('/usr/binphantomjs --version')
exec('phantomjs --version');
shell_exec('phantomjs --version')

all of them return empty, i have checked that the apache user have access to this folder and even moved it using the php exec function. i have tried to run it with both system types (i run Linux redhat 64bit) what else could be my problem ?