function htmlspecialchars (string, quote_style, charset, double_encode) {

    var optTemp = 0, i = 0, noquotes= false;
    if (typeof quote_style === 'undefined' || quote_style === null) {
        quote_style = 2;
    }
    string = string.toString();
    if (double_encode !== false) { // Put this first to avoid double-encoding
        string = string.replace(/&/g, '&');
    }
    string = string.replace(/</g, '&lt;').replace(/>/g, '&gt;');
 
    var OPTS = {
        'ENT_NOQUOTES': 0,
        'ENT_HTML_QUOTE_SINGLE' : 1,
        'ENT_HTML_QUOTE_DOUBLE' : 2,
        'ENT_COMPAT': 2,
        'ENT_QUOTES': 3,
        'ENT_IGNORE' : 4
    };
    if (quote_style === 0) {
        noquotes = true;
    }
    if (typeof quote_style !== 'number') { // Allow for a single string or an array of string flags
        quote_style = [].concat(quote_style);
        for (i=0; i < quote_style.length; i++) {
            // Resolve string input to bitwise e.g. 'PATHINFO_EXTENSION' becomes 4
            if (OPTS[quote_style[i]] === 0) {
                noquotes = true;
            }
            else if (OPTS[quote_style[i]]) {
                optTemp = optTemp | OPTS[quote_style[i]];
            }
        }
        quote_style = optTemp;
    }
    if (quote_style & OPTS.ENT_HTML_QUOTE_SINGLE) {
        string = string.replace(/'/g, '&#039;');
    }
    if (!noquotes) {
        string = string.replace(/"/g, '&quot;');
    }
 
    return string;
}