Code Optimization Tips Part 1

August 31st, 2006

I realized for being a software engineer that I haven’t written much about programming or coding or anything else. I work mostly with PHP and MySQL, but as some of our applications are getting mad traffic now, I’ve been doing every little thing possible to optimize them.

Here’s a few code optimization tips (mostly PHP) that may not seem obvious to everyone:

• $i++ vs ++$i Remeber back in college? There was always some sort of ++i / i++ trick question on exams right? So what’s the main difference? Most of you have been hard coded to use $i++ everytime, however that’s not always the best idea. The post increment (i++) actualy creates a temporary variable in memory to retain the value of i before incrementing. The pre increment (++i) doesn’t do that. It simply increments i. If you want to use the incremented version of i inside your loop only, then you might as well use the pre; it’ll save you a bit of memory.
• using sizeof() or .size() or whatever. How many times have you done this?
  

  for(i=0; i < sizeof(array); i++) {

  While this is technically correct, it isn’t the best solution when the cardinality of array is large. Coding it this way will actually re-calculate the size of the array every time the loop runs; and the functional overhead can get expensive. If possible, you should calculate the size once then compare against that.

• Speaking of functional overhead…Don’t use functions where built in operators will do. For example, this code:
  

  if (strlen($foo) < 5) {

  can be done without all the overhead by using some of php’s natural operations like this:
  

  if(!isset($foo[4])) {

  The difference here is that isset() is built in to the language (it works like + or -) whereas strlen isn’t. (it works like a function you define)

Anyway.. that’s enough for now. I’m taking a vacation this weekend.. but when I get back, I’ll post some other cool things you might not have known.

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