0 if needle
is a null string or not found or if start
is greater than the length of haystack.
By default, the search starts at the first
character of the receiving string (that is, the value of
start is 1),
and continues to the end of the string. You can override this by specifying
start, the point at which the search starts, and
length, the bounding limit for the search.
If specified, start must be a positive
whole number and length must be
a non-negative whole number.