Only convert <, >, &, ' and " for XML?

It seems I have another problem with special character and double quotes and so on after this question that has been solved earlier.

I used to use this function that convert symbol like '&' to numberic code for XML,

function convert_specialchars_to_xmlenties($string) 
{ 

    # in order to convert  <, >, &, ' and ", include them into the square brackes [<\'"&>\x80-\xff]
    $output = preg_replace('/([<\'"&>\x80-\xff])/e', "'&#' . ord('$1') . ';'", $string);

    # return the result
    return $output; 
}

So if my input is Judge-Fürstová Mila & Judge-Fürstová Mila

I will get Judge-Fürstová Mila & Judge-Fürstová Mila

But I think since I am using PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8" to handle all my special characters, so if my input is something like

Judge-Fürstová Mila & Judge-Fürstová Mila

now will returns,

Judge-Fürstová Mila & Judge-Fürstová Mila

Which is incorrect for XML I think.

So I think I should just convert <, >, &, ' and " only but not other special characters like ü or á

Any ideas I how I can do this? Or maybe I have thought/ understood the problem incorrectly and there are other better ways to solve this problem?

EDIT:

I was wrong, as I just changed the function which only converts <, >, &, ' and "

$output = preg_replace('/([<\'"&>])/e', "'&#' . ord('$1') . ';'", $string);

XML still does not accept the converted code below,

Judge-Fürstová Mila & Judge-Fürstová Mila

I cannot think of any other reason why it does that! Any ideas?

You want htmlspecialchars(). Don't let the name throw you off. It by default converts only the characters you've listed.