The original string.
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.
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.
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
FALSE will be returned.