utf8 decode a unicode code point

utfdecode.php

<?php
// convert utf8 character to its unicode code point
function utf8decode($chr){
    switch(strlen($chr)){
        case 1:
            $x = unpack('c',$chr);
            $dec = $x[1] & 127;
            break;
        case 2:
            $x = unpack('c*',$chr);
            $dec = (($x[1] & 31) << 6)
                |   ($x[2] & 63);
            break;
        case 3:
            $x = unpack('c*',$chr);
            $dec = (($x[1] & 15) << 12)
                |  (($x[2] & 63) << 6)
                |   ($x[3] & 63);
            break;
        case 4:
            $x = unpack('c*',$chr);
            $dec = (($x[1] & 7) << 18)
                |  (($x[2] & 63) << 12)
                |  (($x[3] & 63) <<  6)
                |   ($x[4] & 63);
            break;
    }
    return dechex($dec);
}