@Immutable
    public static String str_rot13(String string) {
        int len = string.length();
        StringBuilder sb = new StringBuilder(len);

        for (int i = 0; i < len; i++) {
            char ch = string.charAt(i);

            if ('a' <= ch && ch <= 'z') {
                int off = ch - 'a';

                sb.append((char) ('a' + (off + 13) % 26));
            } else if ('A' <= ch && ch <= 'Z') {
                int off = ch - 'A';

                sb.append((char) ('A' + (off + 13) % 26));
            } else {
                sb.append(ch);
            }
        }

        return sb.toString();
    }
Parses the cslashes bitmap returning an actual bitmap.

@param charset the bitmap string

@return the actual bitmap
exts/jphp-zend-ext/src/main/java/org/develnext/jphp/zend/ext/standard/StringFunctions.java