XMLHttpRequest和PHP

Question

I take inputs from a form. The inputs contains simple arithmetic operation like 2+3. The input is taken properly as far as i can say. Here chunk has small portion of the input from the input field of the form. As you can see when alert(chuck) gives 2+3 (the right thing) but the response that i get after sending the '2+3' to calculate.php as parameter is 2 3 (2 space 3). My calculate.php simply has something like echo $_GET['param'].

I don't have much experience on this topic. What is the problem here?

chunk = theInput.substring(0,3);
alert(chunk); //output is 2+3
document.getElementById("txtHint3").innerHTML = chunk;//output is 2+3
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function(){
if (this.readyState == 4 && this.status == 200) {
    var response = this.responseText;
    alert(response);  // But here output is 2 3
    document.getElementById("txtHint223").innerHTML = response;  // And same here  is 2 3               
        }
};
xmlhttp.open("GET", "calculate.php?param="+chunk,true);
xmlhttp.send();

Answer 1

+ represents a space in the query string. Use encodeURIComponent() to properly encode the value:

xmlhttp.open("GET", "calculate.php?param="+encodeURIComponent(chunk),true);