Use of eval?

[mothra]

I don't have much ajax experience, maybe someone here can help.

I'm working on a script that relies on data from a query to build a bar graph. Everything is working fine, but my kludgy solution makes me shudder a bit. I'm currently making an ajax call to a php script where I pass in the SQL. The PHP queries the database, does some processing with the returned data, and outputs a response that looks something like this...

//php
the_output = "[3, 'a', '#000000'], [6, 'b' , '#111111'], [9, 'c' , '#222222']";

When it returns to the js, I use eval to process this into an array that the bar graph plugin uses.

//js
success: function(return_value){
the_array = eval('new Array(' + return_value + ')');

This works... but it's so ugly I have to believe there's a better way to pass the data between php and the js script (?)


I do need the ajax functionality so I can dynamically load different data sets without reloading the page. Just thought I would mention that, I'm not just using ajax for the sake of using it.

Thanks for any insights...

[Cremator]

I doubt that code works, PHP variables all begin with $.

As for your query, yeah, just write the values in to the javascript

PHP Code:

the_array = [<?php echo $the_output; ?>];

which when viewed in the will look like.

PHP Code:

the_array = [[3, 'a', '#000000'], [6, 'b' , '#111111'], [9, 'c' , '#222222']]; 


an array of arrays.

[mothra]

Don't doubt it, it does indeed work. Chances are I probably just quickly typed that example in and left out a $... it's a crazy world we live in.

Regarding your answer, I don't think you have grasped my question at all. I have no interest in changing the format of the return value. That's the format that my graph plugin expects, and it works correctly as shown in my post.

[felgall]

Why not have the PHP generate it as a JSON string instead and then use JSON.parse() to process it instead of eval().

[mothra]

felgall, that sounds like it's probably the right solution. I don't know anything about JSON however. I'm fairly inexperienced with AJAX in general. Would you mind giving me an example?

Thank you.

[felgall]

ISee http://javascriptexample.net/ajax04.php

[mothra]

Awesome, thank you. I am off to absorb, will update with my findings ........


To follow up, JSON simplified what I wanted to do, and it doesn't look and feel like a total kludge any more. For the sake of anyone else who might read this in the future, this is what I did...

// php
while ($row = mysql_fetch_assoc($result)) {

	$value = $row['val'];
	$label = $row['label'];
	$color = $row['color'];

	$ret_ar[] = array($value, $label, $color);
}

echo json_encode($ret_ar);

// js
success: function(return_value){
dataArrayForGraph = JSON.parse(return_value);

Works great, no more need to build ugly strings to later be used with the dreaded eval function. Thanks to felgall for turning me on to JSON!