php5.3 exec() : output truncate

Hi, I want to get the list of running processes. also, I call exec() with "ps -A" (ps -A displays almost all processes of all users) Unfortunatly, the output of "ps -A" seems incomplete the test file test.php: <?php unset($buf); unset($res); exec("ps -A", $buf, $res); for($i=0; $i < count($buf); $i++) {

    echo($buf[$i]."<br>");

} ?> If I run the test.php under the context of httpd (from http://<server>/test.php), I can see only a subset of running processes (some processes of user "apache") PID TTY TIME CMD 3207 ? 00:00:00 httpd 3359 ? 00:00:00 httpd 3360 ? 00:00:00 httpd 3361 ? 00:00:00 httpd 3362 ? 00:00:00 httpd 3363 ? 00:00:00 httpd 3364 ? 00:00:00 httpd 3365 ? 00:00:00 httpd 3366 ? 00:00:00 httpd 3569 ? 00:00:00 ps If I run the same script directly from php (from user apache) , I can see *all* processes as expected # sudo -u apache php -f test.php

  PID TTY          TIME CMD<br>
    1 ?        00:00:01 init<br>
    2 ?        00:00:00 migration/0<br>
    3 ?        00:00:00 ksoftirqd/0<br>
    4 ?        00:00:00 watchdog/0<br>
    5 ?        00:00:00 events/0<br>
    6 ?        00:00:00 khelper<br>

[...] Is it a problem with exec() or with "ps -A" or with .... ? any ideas ? more information : OS = centos 5.5 # httpd -v Server version: Apache/2.2.3 Server built: Jan 10 2013 08:22:14 # php -v PHP 5.3.3 (cli) (built: Jun 27 2012 12:25:37)