/**
 * Convert a string to an array
 * @param string $str
 * @param number $split_length
 * @return multitype:string
 */
function mb_str_split($str,$split_length=1,$charset="UTF-8"){
  if(func_num_args()==1){
    return preg_split('/(?<!^)(?!$)/u', $str);
  }
  if($split_length<1)return false;
  $len = mb_strlen($str, $charset);
  $arr = array();
  for($i=0;$i<$len;$i+=$split_length){
    $s = mb_substr($str, $i, $split_length, $charset);
    $arr[] = $s;
  }
  return $arr;
}

function mbStrSplit ($string, $len=1) {
  $start = 0;
  $strlen = mb_strlen($string);
  while ($strlen) {
    $array[] = mb_substr($string,$start,$len,"utf8");
    $string = mb_substr($string, $len, $strlen,"utf8");
    $strlen = mb_strlen($string);
  }
  return $array;
}