Oh dear lord and the incompetence of the self-entitled-good-developers. Blockchain is a very different thing from blockchain.info, the site, anyone claiming to produce any good code related to bitcoin shouldn't me distributing this confusion made by the very newbies.
And where did you see anyone confusing Blockchain with Blockchain.info in this thread, other than you of course? I was writing about Blockchain API that was needed for his original solution involving MtGox to verify that the deposit was actually made. This means an API that provides access to the Blockchain. It could be Blockchain.info which provides such API, but it could be bitcoind that provides such API as well or any other tool that provides API to access Blockchain. I was referring to a general category. Reading with understanding is an important skill. It's like if I wrote about “social network website” or “search engine” and you understood it as “Facebook” or “Google” respectively. Please don't confuse Blockchain with Blockchain.info.
MtGox provides a websockets API, so scratch all the "repeatedly" words from your text, as well your line of thought to how to code this.
PHP (which he wanted to use) isn't very suitable tool to continuously run a script, especially if you don't control or at least know the runtime environment (many hosting providers kill PHP scripts that run more than couple of minutes). You need a reliable environment in which your script can be working 24/7 without interruptions if you want to handle an over-hour-long process in a single run. PHP environments usually aren't good for that (unless you control them on your own). Anyway, solution involving MtGox (and requiring either very long runtime or a cron job) wasn't a good one and I suggested changing the design to entirely different one, which doesn't require periodic checks.
Also, there is zero need for PHP here. If the guy wants to continue with a browser-only solution, javascript is enough to provide all he needs.
This is correct. But you need to remember of either not closing the page before the process is finished or you need to use local storage in the browser to keep the data - and then remember to reopen the script to finish the process after deposit has been made.
Blockchain.info wallet API provides a nice callback notifications over HTTP. This way your script can be notified as soon as the deposit is made and finish the second part of the process. This won't be possible using client-side JS only.
Using hosted PHP solution and Blockchain.info API callback, you can start the process by generating a deposit address and then you can send this address to someone else and then close your browser and forget. You don't need to keep your browser open or even be online until that person sends you bitcoins (what might happen half day later). As soon as the other person deposits, Blockchain.info API would notify the script and the script would split bitcoins and distribute them to destination addresses automatically.