AJAX Using JSON, how do I read the object?

[JustinK101]

So I have my php script, which is as follows:

 

<?php
require("pref.php");
require("db_connect.php");

if(!empty($_GET['customer_id']) && $_GET['customer_id'] != "None")
{
	mysql_select_db("yjpalmer_ordermanager");
	$sql = "SELECT order_id FROM orders WHERE associated_customer_id = " . $_GET['customer_id'] . " ORDER BY order_id ASC";
	$result = mysql_query($sql);

	$myArray = array();
	while($row = mysql_fetch_row($result))
	{
		array_push($myArray, $row[0]);
	}

	print(json_encode($myArray));
}
?>

 

A test output of the above script is:

 

["263","285","286","287","288","290","291","292","293","294"]

 

Then my Javascript code is:

 

function updateDependentSelectBox(serverSideScript, objectToRead, queryStringName, objectToAppend)
{	
var the_obj;
document.getElementById('ajax_status').innerHTML = '<img src="includes/ajax.gif" alt="Please Wait...">';
xmlHttp = createAjaxObject();
myValue = objectToRead.value;
xmlHttp.open("GET", serverSideScript + '?' + queryStringName + '=' + myValue + '&sid=' + Math.floor(Math.random() * 1000000), false);

xmlHttp.onreadystatechange=function()
   	{
	if(xmlHttp.readyState==4)
	{
		if (xmlHttp.status == 200)
		{
			the_obj = eval("(" + xmlHttp.responseText + ")");
			for(i = 0; i < the_obj.length; i++)
			{
				objectToAppend.options[objectToAppend.length] = new Option(the_obj[i], false, false);
			}
			setTimeout('document.getElementById(\'ajax_status\').innerHTML = \'\'', 850);
		}
		else 
		{
            	alert("AJAX Error! There Was A Problem Parsing The Following Server Side PHP Script.\n\n" + serverSideScript + "");
		}
        }
};

xmlHttp.send(null);		
}

 

My problem is the following line:

 

the_obj = eval("(" + xmlHttp.responseText + ")");

 

What does eval do? How is the variable the_obj constructed? How do I get my data out of it?

[hitman6003]

What does eval do?

It executes the text passed to it as javascript.

 

http://www.w3schools.com/jsref/jsref_eval.asp

 

How is the variable the_obj constructed?

It's defined at the beginning of execution:

 

var the_obj;

 

It is assigned a value of the result of the eval function.  Then it is added as an option in a select box.

 

How do I get my data out of it?

This script that you are using will not do anything with JSON...it executes javascript returned from the server and appends the result to a select box option group.