Q:

$_GET the value of (&) with AJAX

I have three codes the first one is html:
<html>
<head>
<script type = "text/javascript" src = "AJAX.js"></script>
</head>

<body>
<form method = "GET" >
    <input type = "text" id ="a" ><br>
    <input type = "text" id = "b"><br>
    <input type = "button" value ="click"  onclick = "process()"><br>
    <textarea id = "underbutton" ></textarea><br>
</form>
<body>
</html>

Now javaScript (AJAX) :
function process() {
    if(xmlHttp.readyState==0 || xmlHttp.readyState==4){

        a = document.getElementById("a").value;
                b = document.getElementById("b").value;
        xmlHttp.onreadystatechange = handleServerResponse;
        xmlHttp.open("GET","file.php?a="+a+"&b="+b,true);
        xmlHttp.send();
    }
}

function handleServerResponse (){
    if(xmlHttp.readyState==4 && xmlHttp.status==200)
        {

        response = xmlHttp.responseText;
        document.getElementById("underbutton").innerHTML =  response ;

        }

}

Now php file :
<?php  

echo $_GET['a'].'<br>';
echo $_GET['b'].'<br>';

?>

everything is working but the problem is when I type in the first texbox (a) the word hello and the second (b) the code & and click the button ; it must print out hello&.
but it  prints  hello!!
just hello without &.
I noted that I was sending to php file is this :
file.php?a=hello&b=&.
the last & must be %26 
So to print out & I must send :
file.php?a=hello&b=%26. 
How can I fix that ??

A:

Change in the JavaScript:
- a = document.getElementById("a").value;
- b = document.getElementById("b").value;
+ a = encodeURIComponent(document.getElementById("a").value);
+ b = encodeURIComponent(document.getElementById("b").value);

A:

You have to URL-encode your values:
xmlHttp.open("GET","file.php?a="+encodeURIComponent(a)+"&b="+encodeURIComponent(b),true);

You need this because the parameters in your URL are splitted on '&' and so its like:
a=hello
&
b=
&
*(here could be a third parameter)*

