$output=shell_exec('command 2>&1');

http://www.z01d.com/2008/07/08/how-to-call-linux-shell-commands-from-php-script/

The “2>&1″ bit tells to pipe the standard error to the standard output. Otherwise the standard error may not be outputted by the system and you won’t have a way to troubleshoot your script.

Linux shell commands from php script

php, linux

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