Different user in get_current_user() and exec('whoami') for suexec virtual host

Question

I use SuexecUserGroup for VirtualHost

Script

<?php
echo '<pre>';
var_dump(exec('whoami'));
echo "Current Script Owner: ".get_current_user()."\n";

return 'www-data' in first string and right user 'correct_user' in second string

Created files has user name - www-data

How to create files with user 'correct_user' owner?