@Immutable
    public static Memory substr(String value, int start) {
        int length = value.length();
        if (start < 0)
            start = length + start;

        if (start < 0 || start > length)
            return Memory.FALSE;

        return new StringMemory(value.substring(start));
    }
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