I had (a rather edge case) where Strings::startsWith was called from an Arrays::each closure similar to this:

$string = "12345";

Arrays::each([
    '1234' => "jey"
], function($value, $key) use ($string) {
    if(Strings::startsWith($string, $key)) {
        print_r("match");
    }
});

this would never match, since the key is automagically converted into an integer and strpos($haystack, INTEGER) will never match.