@Alan: Good idea for servers that
serve the specified PHP5, but in my
shop, you can’t assume the hosting
server will have PHP5.

I had the same problem and solved it with this sweet little class:

http://mike.teczno.com/JSON.tar.gz

The usage is as easy as:

require_once(‘JSON.php’);
$json = new Services_JSON();

//encoding an array or object
echo $json->decode(array(‘code’ => ‘0′, ‘message’ =>’Your email address is not valid. Please try again.’));

//same for decoding a string
$obj = $json->decode($json_string);

and if you not sure or don’t mind if your environment is php4 or php5 you can do something like this:

if(!function_exists(‘json_encode’)){
function json_encode($obj){
require_once(‘JSON.php’);
$json = new Services_JSON();
return $json->encode($obj);
}
}

if(!function_exists(‘json_decode’)){
function json_decode($str){
require_once(‘JSON.php’);
$json = new Services_JSON();
return $json->decode($str);
}
}

and you never need to worry about it again!

I used to do something very similar. For example, I’d send back a response that was pipe delimited to separate different sets of data. Then, each set of data was tilde delimited to separate functions to execute, variables, etc.

Then, I discovered JSON. It’s SO much easier. Now, I’m doing something very different. In my PHP, I write the JavaScript code that I want execute, return it to the calling page, and it gets executed.

I’m not sure this is smart or not, but it works VERY well. Since I’m primarily a PHP programmer, I prefer dealing with all the logic in PHP instead of trying to parse it out in JS.