substr Function
substr
extracts a substring from a given string by offset and (maximum) length.
Examples
The offset and length are both counted in unicode characters rather than bytes:
The offset index may be negative, in which case it is relative to the end of the given string. The length may be -1, in which case the remainder of the string after the given offset will be returned.
If the length is greater than the length of the string, the substring will be the length of all remaining characters.