Problem to run java command line with passthru()

Hello, I try to use passthru() command to execute command line in my script. At Telnet I can use following command to execute my java program and out put is fine. $java HelloWorld So, I need to embed this command line in the script like this : //---- java.php ---- <? passthru("java HelloWorld") ; ?> But call through browser its return nothing. no out put , no error display. I test my script by log-in Telnet to call the PHP script directly. $php java.php The out put is right. What should I do ? I try exec() , system() but result is same. Thanks, -- -Tuna-