Zum Basteln ;)
Funktional, 3, 2, 1 Byte, den Rest kannste selber bauen, Codevorlage s.u.

  
<?php  
  
class Codepoint{  
    private function examine($part){  
        static $idx = 1;  
        if( ($part > 223) && ($part < 240)){ // 3 bytes  
            $this->CODEPOINTS[] = ($part - 224 << 12) + ($this->OCTS[$idx + 1] - 128 << 6) + $this->OCTS[$idx + 2] - 128;  
            $idx += 3;  
        }  
        elseif($part > 191 && $part < 224){  // 2 bytes  
            $this->CODEPOINTS[] = ($part - 192 << 6) + $this->OCTS[$idx + 1] - 128;  
            $idx += 2;  
        }  
        else{  
            $this->CODEPOINTS[] = $part;  
            $idx += 1;  
        }  
        return $idx;  
    }  
  
    public function cps($str){  
        $this->OCTS = unpack('C*', $str);  
  
        $this->CODEPONTS = array();  
        for($i = 1; $i <= sizeof($this->OCTS);){  
           $i = $this->examine($this->OCTS[$i]);  
        }  
  
        return($this->CODEPOINTS);  
    }  
}  
  
$c = new Codepoint();  
print_r($c->cps('€äöüA'));  
  
  
  
#StringView.loadUTF8CharCode = function (aChars, nIdx) {  
#  
#  var nLen = aChars.length, nPart = aChars[nIdx];  
#  
#  return nPart > 251 && nPart < 254 && nIdx + 5 < nLen ?  
#      /* (nPart - 252 << 32) is not possible in ECMAScript! So...: */  
#      /* six bytes */ (nPart - 252) * 1073741824 + (aChars[nIdx + 1] - 128 << 24) + (aChars[nIdx + 2] - 128 << 18) + (aChars[nIdx + 3] - 128 << 12) + (aChars[nIdx + 4] - 128 << 6) + aChars[nIdx + 5] - 128  
#    : nPart > 247 && nPart < 252 && nIdx + 4 < nLen ?  
#      /* five bytes */ (nPart - 248 << 24) + (aChars[nIdx + 1] - 128 << 18) + (aChars[nIdx + 2] - 128 << 12) + (aChars[nIdx + 3] - 128 << 6) + aChars[nIdx + 4] - 128  
#    : nPart > 239 && nPart < 248 && nIdx + 3 < nLen ?  
#      /* four bytes */(nPart - 240 << 18) + (aChars[nIdx + 1] - 128 << 12) + (aChars[nIdx + 2] - 128 << 6) + aChars[nIdx + 3] - 128  
#    : nPart > 223 && nPart < 240 && nIdx + 2 < nLen ?  
#      /* three bytes */ (nPart - 224 << 12) + (aChars[nIdx + 1] - 128 << 6) + aChars[nIdx + 2] - 128  
#    : nPart > 191 && nPart < 224 && nIdx + 1 < nLen ?  
#      /* two bytes */ (nPart - 192 << 6) + aChars[nIdx + 1] - 128  
#    :  
#      /* one byte */ nPart;  
#  
#}  
  
?>  

Codepoints sind dezimal, für hex siehe sprintf %X
Array
(
    [0] => 8364
    [1] => 228
    [2] => 246
    [3] => 252
    [4] => 65
)