PHP output: file include vs. function (performance)

Question

Here's two methods to display html output: function vs include. Is there a performance hit when accessing the file system as opposed to accessing memory? If each page load has dozens, or even hundreds of includes, at what point does this become a problem?

Option 1: Html display loop using a function

foreach ($items as $item){
    displayItem($item);
}

function displayItem($item){ ?>
    <html output>
<?php }

Option 2: Html display loop using include

foreach ($items as $item){
    include $path . 'displayItem.php';
}

//inside displayItem.php:
<html output>

The most sure way is to test it yourself on your setup. Though, filesystem is usually cached in memory, so it's the performance of include mechanism itself that matters, rather than FS performance. — aland
– aland, Commented Oct 3, 2012 at 17:47
In general, the performance bottleneck of a PHP site is not in the includes. Some libraries have hundreds of includes and are used in very high traffic sites. You should organise the code in your site in order to structure it correctly, rather than focusing on the speed. If you're worried about the performance of your site, run a profiler and find our what the real bottlenecks are in your code. — Spudley
– Spudley, Commented Oct 3, 2012 at 17:56

rid · Accepted Answer · 2012-10-03 17:48:09Z

2

Sure, disk access is much slower than memory access, that's why disk accesses are usually cached in memory by the operating system. Even so, if you could somehow cache the output of displayItem() (which could include a file) then save and load the cached output from memory with something like memcache, you should see significant increases in performance.

answered Oct 3, 2012 at 17:48

rid

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3 Comments

Michael Lewis Over a year ago

Well, I wouldn't want to cache the output of displayItem, because it would be different for each $item. I'm wondering if this is an acceptable format for creating ALL my (dynamic) output code. For example, I could then use the file explorer to view all my displaySmallList vs displaySmallListNoImage, and all other variations. I could organize them in folders. The number of includes would be very high. The question is, is the file accessed once, and like a function, stored in memory, and not accessed again by the file system? I'll have to read Brad's link when I have more time...

rid Over a year ago

@MikeLewis, sure you can, you could make a cache for each item or even a cache for each page. This is a pretty common practice. But for accessing files, it depends on the filesystem, the OS, the available memory and the physical HDD (which also does some caching of its own). Alternatively, you can store everything in a ramdisk if the information can be re-generated. But if you have many items, depending on how many you display on a page vs. the total number, it's likely better to read each item from an individual file than to load everything in memory at once for each request.

rid Over a year ago

@MikeLewis, as you can see, there are many variables here, so it's always best to benchmark if you can, since your situation may be different from someone else's. I did actually have a situation once when disk reads were the bottleneck, but it's uncommon. I recommend taking a look at xhprof or xdebug which both can generate very nice and useful profiling data.

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