Converting named HTML entities to numeric HTML entities

Question

Is there a PHP function to convert named HTML entities into their respective numeric HTML entities?

For example:

$str = \"Oggi è un bel&am         


        

Answer 1

This one

1. does not require enumeration of entities in user's code,
2. works on HTML code containing named entities (rude applying html_entity_decode to the whole string messes up < and > (converted < and >) and HTML tag start/end):

Here it is

function htmlent2xml($s) {
    return preg_replace_callback("/(&[a-zA-Z][a-zA-Z0-9]*;)/",function($m){
       $c = html_entity_decode($m[0],ENT_HTML5,"UTF-8");
       # return htmlentities($c,ENT_XML1,"UTF-8"); -- see update below

       $convmap = array(0x80, 0xffff, 0, 0xffff);
       return mb_encode_numericentity($c, $convmap, 'UTF-8');
    },$s);
}

upd: Following Carlos's remark, the proposed solution is fixed using this answer to get the required numeric entities.