shell_exec() return nothing

[hvle]

I ran into a problem with shell_exec()

PHP and all files hosting on Redhat

 

I have a html page that allow me to enter a linux command, then submit, then I get the output print out between <pre>$output</pre>

 

when enter command: ls -l /etc, it a list of file and directory on /etc as expected

however, when I tried to execute my program at /etc/earch/esearch (esearch is executable), I received nothing back.

 

however when I telnet to server, command /etc/earch/esearch does return some text.

i'm sure php was running as same user as telnet.

 

no clue, any help would be greatly appreciated.