calling external programme (exec(), system())

[bumbar]

hi! I write very, very simple script who call external program. The script is run on Linux Slackware, Apache/1.3.37 (Unix) mod_ssl/2.8.28 OpenSSL/0.9.8b PHP/4.4.4

here is my script:
<?php
echo exec('ls');
?>
this work properly.

but if i write:

<?php
echo exec('xine'); //xine is a multimedia player
?>

not work! where is my problem?

Thanks!

[altexis]

The problem is that apache can run console applications.. not multimedia ones.