How to manually enter POST data into browser

Question

I'm debugging my php script and need to try to post data to by manually inputting it into the URL in my browser.

The javascript which sends the request is below. How do I enter the correct data into my browser so it's encoded in the same way as the javascript function? I tried encoding the string with http://meyerweb.com/eric/tools/dencoder/ and putting sendmail.php?q="the encoded string"... but that didn't work. Do I have to add more information?

function SendPHP(str, callback){
    xmlhttp = new XMLHttpRequest();  
    str = "q=" + encodeURIComponent(str);

    xmlhttp.open("POST","sendmail.php", true);
    xmlhttp.onreadystatechange=function(){
        if (xmlhttp.readyState == 4){
                      inProgress=false;
            if(xmlhttp.status == 200){
                            callback(xmlhttp.responseText);
            }
        }
    };
    xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");  
        if (inProgress==false){
        inProgress=true;
        xmlhttp.send(str);
        }
        else{
            writeDisplayConsole("ERROR: xmlhttp fired twice!");
        }
}

Answer 1

Use the Chrome Rest plugin extension https://chrome.google.com/webstore/detail/advanced-rest-client/hgmloofddffdnphfgcellkdfbfbjeloo