(PHP 5, PHP 7)
iconv_substr — Cut out part of a string
$str
   , int $offset
   [, int $length = iconv_strlen($str, $charset)
   [, string $charset = ini_get("iconv.internal_encoding")
  ]] )
   Cuts a portion of str specified by the 
   offset and length parameters.
  
strThe original string.
offset
       If offset is non-negative,
       iconv_substr() cuts the portion out of
       str beginning at offset'th
       character, counting from zero.
      
       If offset is negative,
       iconv_substr() cuts out the portion beginning
       at the position, offset characters
       away from the end of str.
      
length
       If length is given and is positive, the return
       value will contain at most length characters
       of the portion that begins at offset
       (depending on the length of string).
      
       If negative length is passed,
       iconv_substr() cuts the portion out of
       str from the offset'th
       character up to the character that is
       length characters away from the end of the string.
       In case offset is also negative, the start position
       is calculated beforehand according to the rule explained above.
      
charset
       If charset parameter is omitted,
       string are assumed to be encoded in
       iconv.internal_encoding.
      
       Note that offset and length
       parameters are always deemed to represent offsets that are
       calculated on the basis of the character set determined by
       charset, whilst the counterpart
       substr() always takes these for byte offsets.
      
   Returns the portion of str specified by the
   offset and length parameters.
  
   If str is shorter than offset
   characters long, FALSE will be returned.