function getsortby(el, form){    
    var pars = "choose="+el.value;
    var url = '/ajax/choose_select.php';
	var myAjax = new Ajax.Request(
        url, 
        {method: 'get', parameters: pars, onFailure: reportError, onComplete: function(r){makesortby(r,form)}});      
           
}
function makesortby(r,form){    
    if (r.responseText) {
        var sortbyar = eval(r.responseText);               
        form.sortby.options.length=0;    
        for(var i=0; i<sortbyar.length; i++) {
            form.sortby.options.add(new Option(sortbyar[i].name, sortbyar[i].num));
        }
    }
}