This function is available as
Str\search_last() in Facebook's www repository.
Returns the last position of the "needle" string in the "haystack" string, or null if it isn't found
namespace HH\Lib\Str; function search_last( string $haystack, string $needle, int $offset = 0, ): ?int;
An optional offset determines where in the haystack (from the beginning) the search begins. If the offset is negative, the search will begin that many characters from the end of the string and go backwards. If the offset is out-of-bounds, a ViolationException will be thrown.
Previously known in PHP as
int $offset = 0