(PHP 4 >= 4.0.6, PHP 5)
mb_convert_variables — Convert character code in variable(s)
$to_encoding
   , mixed $from_encoding
   , mixed &$vars
   [, mixed &$...
  ] )
   Converts 
   character encoding of variables vars in
   encoding from_encoding to encoding 
   to_encoding. 
  
mb_convert_variables() join strings in Array or Object to detect encoding, since encoding detection tends to fail for short strings. Therefore, it is impossible to mix encoding in single array or object.
to_encodingThe encoding that the string is being converted to.
from_encoding
       from_encoding is specified as an array 
       or comma separated string, it tries to detect encoding from
       from-coding. When from_encoding 
       is omitted, detect_order is used.
      
vars
       vars is the reference to the
       variable being converted. String, Array and Object are accepted.
       mb_convert_variables() assumes all parameters
       have the same encoding.
      
...
       Additional vars.
      
   The character encoding before conversion for success, 
   or FALSE for failure.
  
Example #1 mb_convert_variables() example
<?php
/* Convert variables $post1, $post2 to internal encoding */
$interenc = mb_internal_encoding();
$inputenc = mb_convert_variables($interenc, "ASCII,UTF-8,SJIS-win", $post1, $post2);
?>