Interpreting JavaScript in PHP

Question

I'd like to be able to run JavaScript and get the results with PHP and is wondering if there is a library for PHP that allows me to parse it out. My first thought was to use node.js, but since node.js has access to sockets, files and things I think I'd prefer to avoid that.

Rationale: I'm doing screen scraping in PHP and have encountered many scenarios where the data is being produced by JavaScript on the frontend, and I would like to avoid writing specialized filtering functions to act on the JavaScript on a per-case basis since that takes a lot of time. The more general case would be to parse the JavaScript directly.

Downvoting: I don't really see what's so controversial about this question, modern web crawlers are known to do it, the only difference is that they tend to not be written in PHP. [1]

[1] http://blogs.forbes.com/velocity/2010/06/25/google-isnt-just-reading-your-links-its-now-running-your-code/

Answer 1

It's an interesting question and the down-voters are being unimaginative about potential use-cases. Page archiving tools, printing scripts, preview images - all valid reasons to want to manipulate a document with the JavaScript included within the page.

I'm not aware of any existing PHP implementations, but you could probably adapt Mozilla's SpiderMonkey as a PHP module, or as a standalone tool to manipulate a DOMDocument and return the result.

I haven't had experience with server-side JavaScript, but some issues that I believe might need to be dealt with:

• Host objects like document and window are not part of the ECMAScript specification (these are objects provided by the implementing browser) so you need to make sure that the library provides equivalent host objects.
• You might have security issues around executing client side scripts within a server side environment. This is a lot like allowing the user to submit a PHP script to be evaluation, so you need to make sure the security sandbox is tight.

Another (perhaps) safer and easier to implement option might be to use a modified FireFox or WebKit instance that runs as a browser, loading up the target pages and returning the modified source to your application.