PHP IF Statement Evaluation & Server Overhead

Question

I'm curious what the impact on the server is when PHP if statements are evaluated, i.e. memory consumption and CPU usage and if this could become a major issue as traffic grows?

For example, if I use a lot of PHP IF statements in the theme for each post summary on a WordPress blog, is this going to require a great deal more server resources if the home page starts getting high traffic? And, on pages where many posts are listed (i.e. category pages) , it seems like this could become a problem.

I'm thinking it may be good idea to pare down the IF statements that aren't absolutely necessary in the event that traffic spikes. Or, is this even something I be worrying about?

Answer 1

I think this is something you don't have to worry about : if your application does one or two queries to the database, those will take much more time than a couple (even more than a couple) of "if".

This is kind of "micro-optimization" : if you are looking for big optimizations in the event of a traffic spike, there are other ways that should be explored first ;-)

For some (quite longer) explanations / ideas, you can take a look at this answer I gave yesterday to another question.
(I really don't feel like rewriting any of that before at least a couple of days have passed ^^ )

Basically, what can really help is :

• Using an opcode cache, like APC
• Using caching : the more data you cache, the less calculations / DB queries you have to make -- and those are the one that generally take the most important amount of time
• Using Xdebug and it's profiling abilities, to identify what takes time in your application
• Optimizing SQL queries, using the right indexes
• If you want to go farther, you can use a reverse-proxy to act as another level of cache ; for instance, varnish.

Answer 2

The time spent evaluating 1000s of if statement will be completely overwhelmed by a single database query.

You need to:

1. Profile to find out where your bottlenecks are
2. Focus - if a function takes 50% of the total time then making it 10% faster will have more effect than making a teeny function 90% faster.

Edit:

Database queries are slow (even a quick one) - you should aim to make as few queries as possible, within reason. Within a query, I don't think there's a speed difference between checking for NULL or a specific value - if there is it will be a minuscule difference.

Answer 3

Nothing to worry about, at all.

Answer 4

I'm thinking we need to give a more logical reason why it doesnt matter.... it's because an IF statement at it's basic level in assembler comes down the the JNZ mnemonic. It's a 1 "word" value meaning "JUMP IF NOT ZERO". The real heavy load will come from the comparing and evaluating the conditionals, not the IF statement itself.