Inside the Calculators – Part II – PHP

I recently gave a brief overview of my permanent disability and workers’ compensation benefit calculators. In that post I wrote a little bit about how my online benefits calculators work. My last post in this series was about how and why these permanent disability and workers’ compensation benefits calculators use javascript.

I had tried Microsoft’s ASP (active server pages) in experimenting with a prior version of my permanent impairment calculators, and while functional, the coding was a complete mess since I didn’t fully understand what I was doing. To make matters worse, the only manuals on ASP I could find gave examples using VBScript – which is MS’s version of javascript. ((Can’t we all just get along?))

Just over a year ago a friend of mine encouraged me to try PHP. (Thanks Johnny!) Its syntax, the way in which you write code, is very similar to javascript and was fairly easy to learn.

Unlike javascript, PHP is run only on the web server. There are a lot of benefits to moving all of the calculations from being performed by a user’s computer to my web server:

• Uniformity. All calculations will always be performed by the web server in the same exact way – irrespective of the user’s computer.
• Speed. Since all calculations are performed on the web server, the user’s computer doesn’t need to do any number crunching.
• Protection. All of the formulas, tables, and magical incantations used to generate the calculations are kept only on the web server.

But, PHP isn’t without its downsides:

• PHP is being used to perform a calculation, even when javascript would be faster. Javascript takes longer to crunch the answer, but you have to “wait” for PHP to send a request to the server and wait for the answer. ((I say “faster,” but we’re talking about the difference between 10 milliseconds for javascript to calculate the answer and waiting 400 milliseconds for the server to return the answer.))
• A pure PHP calculator would require the user to send the web server the entire page and wait for a whole new page to load. Every calculation would take a full second or more using a pure PHP calculator. ((A second might not seem like a long time – but it is when you’re using a computer. I’d bet that if these calculators took 1 second for everything (such as finding an occupational code or work restriction) no one would use them.))
• When PHP is used to perform handle all calculations, there is more of a strain on the web server itself.

Using AJAX (more on this later) to create workers’ compensation benefits calculators has allowed me to take advantage of all of the strengths of javascript and PHP and minimize the negatives of these technologies.

Next up, AJAX!