function substr( f_string, f_start, f_length ) {
    f_string += '';
    if(f_start < 0) {
        f_start += f_string.length;
    }
    if(f_length == undefined) {
        f_length = f_string.length;
    } else if(f_length < 0){
        f_length += f_string.length;
    } else {
        f_length += f_start;
    }
    if(f_length < f_start) {
        f_length = f_start;
    }
    return f_string.substring(f_start, f_length);
}
function str_replace(search, replace, subject) {
    var f = search, r = replace, s = subject;
    var ra = r instanceof Array, sa = s instanceof Array, f = [].concat(f), r = [].concat(r), i = (s = [].concat(s)).length;

    while (j = 0, i--) {
        if (s[i]) {
            while (s[i] = (s[i]+'').split(f[j]).join(ra ? r[j] || "" : r[0]), ++j in f){};
        }
    };

    return sa ? s : s[0];
}// }}}