Beginner question about AJAX

[asmon]

I'm a PHP programmer but i'm pretty messed up at this moment with the following script.
I have a page with a 'TEXTAREA' and a 'PLAY' text.
when i click PLAY, values are being displayed in the TEXTAREA with a delay of a second.
the values are stored in array, if for example i have an array with the values (2,5,7,8) then it will first show 2, after a second 4 and so on...

the values are being set using PHP, then i convert the php array into JS array so i can execute the script above.
the problem is i need those values to be stored in the database only after
the user has pressed 'PLAY'.
see where the problem is?

I've just started reading about ajax so i don't really know how it works and what i am able to do with it. just sending back the JS array and then executing the query is a bad idea because the values can be easily changed by the client .

i guess i first need to only put the TEXTAREA and the PLAY button.
then when the user press PLAY, i have to run a php code with all the calculations and stuff and only then sending the JS script back to the user.
i am not sure how it works, i know the data you retrieve using AJAX is XML type or something like that. am i able to send a new JS code directly back to the user?

I know the question looks like a big mess with my English, sorry about that...

[johnhjohn]

Here is the javascript necessary to perform this function

var xmlHttp;
function GetXmlHttpObject()
{
var xmlHttp=null;
try
 {
 // Firefox, Opera 8.0+, Safari
 xmlHttp=new XMLHttpRequest();
 }
catch (e)
 {
 // Internet Explorer
 try
  {
  xmlHttp=new ActiveXObject('Msxml2.XMLHTTP');
  }
 catch (e)
  {
  xmlHttp=new ActiveXObject('Microsoft.XMLHTTP');
  }
 }
return xmlHttp;
}


function send_request()  // call this function to send information
{
xmlHttp=GetXmlHttpObject();
if (xmlHttp==null)
  {
  alert ('Browser does not support HTTP Request');
  return;
  } 

var url='yourpage.php';  // use the php page you are going to send information to

xmlHttp.onreadystatechange=stateChanged;
xmlHttp.open('POST',url,true);  // uses post method
xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xmlHttp.send('yourpostvariable='+javascriptvariable);  // will send value as POST (use $_POST['yourpostvariable'] to get this value)
}

function stateChanged() 
{ 
if (xmlHttp.readyState==4 || xmlHttp.readyState=='complete')  // used for determining if AJAX function is complete
 { 
 var response=xmlHttp.responseText;  // response from php page
 alert(response);  // this will alert the response from the php page (you may use eval or an if statement to perform functions
 } 
}

Here is possible php code:
[PHP]
<?php

$variable = $_POST['yourpostvariab le']; // get post variable from javascript
if($variable == "somevalue" )
{
echo "one"; // this will be return to the javascript and will be alerted
} else {
echo "two"; // this will be return to the javascript and will be alerted
}

Hope I helped :)
?>
[/PHP]

[asmon]

ahmm for some reason i can't make it work.
in my page i put

<script type="text/javascript" src="something. js">
send_request()
</script>


and changing 'var url' in something.js
I think it's enough for maknig your example work, what else am i missing?

There is something else i'm wondering about. in the guide i'm reading right now it says i need to send the response as XML.
[PHP]<?php
header('Content-Type: text/xml');
echo '<?xml version="1.0" encoding="UTF-8" standalone="yes "?>';
echo '<response>';
......
echo '</response>';
?>
[/PHP]

by your example i can see i don't have to do that, can you please explain about this?

thank you.

[johnhjohn]

I have heard about the use of xml, but I discovered this way of completing this task, so I decided not to learn the xml way of doing this.

Are the functions not working?
If so, tell me what's happening and I can try to ix the problem.

Thanks.