PHP performance

Question

What can I do to increase the performance/speed of my PHP scripts without installing software on my servers?

Answer 1

Profile. Profile. Profile. I'm not sure if there is anything out there for PHP, but it should be simple to write a little tool to insert profiling information in your code. You will want to profile function times and SQL query times.

So where you have a function:

function foo($stuff) {
    ...
    return ...;
}

I would change it to:

function foo($stuff) {
    trace_push_fn('foo');
    ...
    trace_pop_fn('foo');
    return ...;
}

(This is one of those cases where multiple returns in a function become a hinderance.)

And SQL:

function bar($stuff) {
    trace_push_fn('bar');

    $query = ...;
    trace_push_sql($query);
    mysql_query($query);
    trace_pop_sql($query);

    trace_pop_fn('bar');
    return ...;
}

In the end, you can generate a full trace of the program execution and use all sorts of techniques to identify your bottlenecks.

Answer 2

One reasonable technique that can easily be pulled off the shelf is caching. A vast amount of time tends to go into generating resources for clients that are common between requests (and even across clients); eliminating this runtime work can lead to dramatic speed increases. You can dump the generated resource (or resource fragment) into a file outside the web tree, and then read it back in when needed. Obviously, some profiling will be needed to ensure this is actually faster than regeneration - forcing the web server back to disk regularly can be detrimental, so the resource really does need to have heavy reuse.

You might also be surprised how much time is spent inside badly written database queries; time common generated queries and see if they can be rewritten. The amount of time spent executing actual PHP code is generally pretty limited, unless you're using some sub-optimal algorithms.

Neither of these are limited to PHP, though some of the PHP "magicy" approaches/functions can over-protect one from thinking about these concerns. For example, I recently updated a script that was using array_search to use a binary search over a sorted array, and gained the expected exponential speedup.