(PHP 4 >= 4.0.6, PHP 5)
mb_detect_encoding — Detect character encoding
$str
   [, mixed $encoding_list = mb_detect_order()
   [, bool $strict = false
  ]] )
   Detects character encoding in string str. 
  
strThe string being detected.
encoding_list
       encoding_list is list of character
       encoding. Encoding order may be specified by array or comma
       separated list string.
      
       If encoding_list is omitted,
       detect_order is used.
      
strict
       strict specifies whether to use
       the strict encoding detection or not.
       Default is FALSE.
      
   The detected character encoding or FALSE if the encoding cannot be
   detected from the given string.
  
Example #1 mb_detect_encoding() example
<?php
/* Detect character encoding with current detect_order */
echo mb_detect_encoding($str);
/* "auto" is expanded according to mbstring.language */
echo mb_detect_encoding($str, "auto");
/* Specify encoding_list character encoding by comma separated list */
echo mb_detect_encoding($str, "JIS, eucjp-win, sjis-win");
/* Use array to specify encoding_list  */
$ary[] = "ASCII";
$ary[] = "JIS";
$ary[] = "EUC-JP";
echo mb_detect_encoding($str, $ary);
?>