:sig
bool contains(String haystack, String needle)

:params
haystack : string to search in
needle : substring to look for
return value : `true` when `needle` appears in `haystack`, otherwise `false`

:see
>string

:content
Returns whether `haystack` contains `needle`.

An empty `needle` always returns `true`.

## Related Concepts

- PHP: `str_contains()`
- JavaScript / Node.js: `String.prototype.includes()`