如何在服务器文件（如php）不存在时创建ajax请求？

i was developing sharetronix script but there is something realy odd about this script i can see in console network request goes for example for this address

http://localhost/ajax/postform-submit/ajaxtp:xml/r:0

but i cant find any folder with postform-submit name.i know this is possible with redirection using htaccess but i cant find anything in htaccess file.

this is part of js code where this request send

function postform_submit_step4()
{
    var req = ajax_init(true);
    if( ! req ) { return; }
    var p   = "post_temp_id="+encodeURIComponent(pf_data.temp_id)+"&message="+encodeURIComponent(pf_data.message);
    if( pf_data.existing_post_id != "" ) {
        p   += "&editpost="+encodeURIComponent(pf_data.existing_post_id);
    }
    else if( pf_data.share_with_type == "user" ) {
        p   += "&username="+encodeURIComponent(pf_data.share_with_xtra);
    }
    else if( pf_data.share_with_type == "group" ) {
        p   += "&groupname="+encodeURIComponent(pf_data.share_with_xtra);
    }
    if( pf_data.at_link[0] ) {
        p   += "&at_link="+encodeURIComponent(pf_data.at_link[0]);
    }
    if( pf_data.at_image[0] ) {
        p   += "&at_image="+encodeURIComponent(pf_data.at_image[0]);
    }
    if( pf_data.at_file[0] ) {
        p   += "&at_file="+encodeURIComponent(pf_data.at_file[0]);
    }
    if( pf_data.at_videoembed[0] ) {
        p   += "&at_videoembed="+encodeURIComponent(pf_data.at_videoembed[0]);
    }
    req.onreadystatechange  = function() {
        if( req.readyState != 4  ) { return; }
        if( ! req.responseXML ) { return; }
        var data    = req.responseXML.getElementsByTagName("result");
        if( !data || !data[0] ) { return; }
        data    = data[0];
        var status  = data.getElementsByTagName("status");
        var message = data.getElementsByTagName("message");
        if( !status || !status[0] || !message || !message[0] ) {
            return;
        }
        status  = status[0].firstChild.nodeValue;
        message = message[0].firstChild.nodeValue;
        if( status != "OK" ) {
            d.getElementById("pf_postederror_msg").innerHTML    = message;
            postform_htmlobject_hide("pf_posting");
            postform_htmlobject_show("pf_postederror", 36);
            postform_htmlobject_show("pf_mainpart", 114, function() { pf_open_state=1; pf_post_state=3; d.post_form.message.disabled=false; d.post_form.message.focus(); });
            return;
        }
        d.getElementById("pf_postedok_msg").innerHTML   = message;
        postform_htmlobject_hide("pf_posting");
        postform_htmlobject_show("pf_postedok", 36, function() { pf_open_state=0; pf_post_state=1; postform_statusmsg_setTimeout(); });
        var btn = d.getElementById("postform_open_button");
        if(btn) {
            btn.style.display   = "";
        }
        if( posts_synchronize ) {
            posts_synchronize();
        }
        var pinf    = pf_data.existing_post_id;
        if( pinf != "" ) {
            pinf    = pinf.split("_");
            var tmp = w.location.href.toString();
            tmp = tmp.replace(/^http(s)?\:\/\//, "");
            tmp = tmp.substr(tmp.indexOf("/"));
            var mtch    = "/view/"+(pinf[0]=="public"?"post":"priv")+":"+pinf[1];
            if( tmp.substr(0,mtch.length)==mtch ) {
                if( viewpost_synchronize ) {
                    viewpost_synchronize();
                }
                else {
                    w.location.href = w.location.href.toString();
                }
            }
        }
    }
    req.open("POST", siteurl+"ajax/postform-submit/ajaxtp:xml/r:"+Math.round(Math.random()*1000), true);
    req.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    req.send(p);
}

how is this possible when there is no redirection?