UTF8 string length counter

The best way to determine the character count of a UTF8 string.

function strlen_utf8( $str )
{
   return mb_strlen( $str, 'UTF-8' );
}
 
//or...
function strlen_utf8( $str )
{
   $c = 0;
   $len = strlen( $str );
   for ( $i = 0; $i < $len; $i++ ) {
      //0x80 = 128
      $ord = ord( $str[$i] );
      if ( $ord & 0x80 ) {
         $ord <<= 1;
         while ( $ord & 0x80 ) {
            $i++;
            $ord <<= 1;
         }
 
         $c++;
      }
      else {
         $c++;
      }
   }
 
   return $c;
}