if (isset($_POST['realname']) && $_POST['realname']!="" &&
 isset($_POST['nickname']) && $_POST['nickname']!="" &&
 isset($_POST['email']) && $_POST['email']!="" &&
 isset($_POST['pass1']) && $_POST['pass1']!="" &&
 isset($_POST['pass2']) && $_POST['pass2']!="" &&
 isset($_POST['phone']) && $_POST['phone']!="" &&
 isset($_POST['address']) && $_POST['address']!="")
{
// Some content here
}
else
{
// Different content here
}

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