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Facebook Credits, the Order ID, and dealing with large integers in 32 bit PHP

So, currently at work I’ve been rewriting all our Payment Gateways for Your Members. Making them more better Class based an abstracting out the common functions to a base class, to save memory footprint and code etc.

And came across a problem when rewriting the Facebook Credits handler.

The order ID that gets passed around, as well as the Application ID is too long for a 32 Bit PHP installation to handle when treating it as an Integer.

So a number like “239724439419867” was ending up as “1.7592246582797E+14” when stored/processed, or converted to a string.
Now the obvious way to process this is to convert it to a string another way, which is somewhat difficult since before you even start it is in a format that you can’t handle.

The saving grace here is the fact that data is passed to you as a JSON packet (aside from the fact the Order ID is in the $_POST variable and thus a string, so I could of used it from there).

This led to me to look at the JSON packet, which starts as a string but when decoded the large integers are still a larger integer than can be processed (whether you json_decode to a Array or to an Object, the problem persists). So I thought about how to process the raw JSON packet and make sure the order ID, and other large integers are treated as strings.

If you look at a Raw JSON packet you can easily spot whats a string, integer, object or array.

Take this example Facebook Credits JSON Packet, (wrapped for readability):

{"order_id":239724439419867,"buyer":197803678,"app":148748711865470,
"receiver":197803678,"amount":5,"update_time":1320075413,
"time_placed":1320075408,"data":"","items":[{"item_id":"<item_id>","title":"Post",
"description":"A New Purchasable Post",
"image_url":"<some url>","product_url":"<some other url>",
"price":5,"data":"<data>"}],"status":"<status>"}
  • order_id is an integer as it has no ” around it
  • status is a string as its surrounded by “
  • Items is an array as its surrounded by [, in this case containing a single object, entries/items are comma separated.

So after thinking about this I decided the best way to sort this out was to convert the integers in the raw JSON packet to strings before decoding.

In pseudo code.

Lop off the { and } from the start and end
Explode around ,
array walk each item
split on :
check if there are no " in the second bit
if none wrap in "
glue back together

Something alone the lines of:

function largeint($rawjson) {
  $rawjson = substr($rawjson, 1, -1);
  $rawjson = explode(',' , $rawjson);
  array_walk($rawjson, 'strfun');
  $rawjson = implode(',', $rawjson);
  $rawjson = '{', . $rawjson . '}';
  $json = json_decode($rawjson);
  return $json;
}

function strfun(&$entry, $key) {
  $data = explode(':', $entry);
  if (FALSE === strpos($data[1], '"')) {
    $data[1] = '"' . $data[1] . '"';
    $entry = implode(':', $data);
  }
}

I’m not sure in terms of memory footprint if its cheaper to do a substr of $data[1] and check if its a ” or not.
I suppose it could test the string length of the detected integer to see if its invalid/unable to process, but then you would be performing a string function on an integer and again the problem would arise.

But as a block of code is does the job, its obviously not ideal for all situations, since in this case I want the integer as a string, I’m not using it for math, but if I did, we probably need to do some bizarre unpack-ing or something.

Any opinions or improvements give us a comment below 😀

Travels of a Commercial WordPress Plugin Developer 1

My job at the moment is updating and coding YourMembers, which is a commercial plugin for WordPress.

Recently I’ve been working on a method to Auto Upgrade the plugin, since commercial plugins cannot go on Extend, and there is no commercial equivalent. Extend being the WordPress plugin repository.

Commercial plugins get no nice little “Plugin needs updating Circle” on the plugins tab, or a nice little message on the plugins page, let alone access to the auto updater!

Which leaves us (commercial plugin devs) to write our own version checkers and hook in accordingly.

So now I have a nice little PHP class which will detect whether it can fwrite/rename and if not if it can FTP instead, much the same as the WordPress updater does.

Now this is all well and good, but I needed a method to download and unzip the new plugin file. Grabbing the file is easy, either file_get_contents (heaven forbid), or curl (yay for curl), and write the file (being a zip) to the web servers temporary directory and process from there.

Now the problem here is how to unzip. A Brief look at how WordPress does it seems to show it has three different methods of unzipping. So dump that.

Didn’t feel the need to use PHP’s ZipArchive class, since I don’t need to edit the zip, just extract its contents.

Off to php.net I go and I find some nice handy functions, and quite surprised to find that the zip_read function can handily recurs into directories within the zip file to return their paths/names. Mildly annoying at the time as I had gone and written a recur loop to go inside directories…. and got thrown a error, nice headdesk moment!

So basically the Zip functions, the basic ones of PHP, are actually quite nice, handy and useful!

Heres my code snippet:

<?php
class someclass() {
	private function unpack() {
		$from = $this->tmp_write;
		$to = $this->tmp_out;
		@mkdir($to);
		
		$zip = zip_open($from);
		if (is_resource($zip)) {
			$this->readzip($zip);
			zip_close($zip);
		} else {
			// failed to open
			$this->error = 1;
		}
	}
	
	private function readzip($zip) {
		$from = $this->tmp_write;
		$to = $this->tmp_out;
		
		echo '</pre><textarea style="width: 100%; height: 100px;">';
		
		while (FALSE !== ($file = zip_read($zip))) {
			$name = zip_entry_name($file);
			echo $name . "\n";
			if (!strpos($name, '.')) {
				// is dir
				@mkdir($to . '/' . $name);
			} else {
				// it recurs into directorys on its own!
				$item = zip_entry_open($zip, $file);
				$size = zip_entry_filesize($file);
				
				$read = zip_entry_read($file, $size);
				$fp = fopen($to . '/' . $name, 'w');
				fwrite($fp, $read);
				fclose($fp);
			}
		}
		
		echo '</textarea><pre>';
	}
}
?>

I just installed this code snippet plugin, which I might need to change its background colours…..

Any suggestions for code snippet plugins greatly appreciated!