manual:
string exec ( string command [, array output [, int return_var]])
exec() executes the given command, however it does not output anything. It simply returns the last line from the result of the command. If you need to execute a command and have all the data from the command passed directly back without any interference, use the passthru() function.
tady na wz je to zakazane. navic tady exe soubor nesputis protoze linux
samozrejme se ten zadany prikaz provede na serveru