PHP "require" Performance
gazehawk.com
gazehawk.com
Things in favor of Autoload:
1) Ease-of-use of not worrying about if your class is available
2) If you don't use Autoloading and require clases, you have to load all of those from the opcode cache (and make APC keep track of them) despite that you may not be using many of those classes at all.
3) It helps encourage putting things in classes (whether they are static functions or not).
4) If you ever need to conditionally require a class, you are likely going to run into the same opcode cache hits (instead of NOPs) as Autoload. You'll have to include ALL of your classes to avoid the problem.
Edit: I looked at the implementation. require_once/include_once unconditionally opens the file, whether it has been loaded already or not. Attempting to follow that path through about 10 levels of indirection (seriously), at some point the PHP implementation passes its notion of the path back to Zend, which suggests possible abspath() etc. Also somewhere in PHP's streams.c I see it unconditionally seek()ing the new file too.
If nothing else, then the layers of crap I just trawled through might cause some slowness, if not some heavy library call like abspath().
I just remembered why I stopped using PHP. :)
require_once("/foo/bar/baz/random/crap/foo.php");
The above requires 5 lstat(2) system calls thanks to realpath() and a typical WordPress-MU page load for us was calling lstat over 5k times. Over NFS that's 5k round trips to the server for every page load. Thankfully there is a knob you can tune in PHP 5.1.x (realpath_cache_size) that caches all those lstats, but as usual, the default is (16K) is too small to be of any use.
I thought they fixed that.
Anyway, just use function_exists instead.
Turns out we didn't need require_once anyway, all but a couple of includes in our entire codebase were in that one area.
I'm not going to say PHP is the greatest language every invented, and in fact I am a huge fan of Python. But I do not think PHP deserves the "In a good language..." treatment. It is a language that is getting better everyday, with a strong and vibrant development community and massive user adoption. It is a good language.
Especially with a Rails-like framework like CakePHP, I find that my programing time is lessened dramatically because of the framework, and my processing time is much lower than Rails because most of the servers I work on are optimized out the wazoo for PHP instead of Ruby.
But your mileage may vary.
A language whose maintainers decided that, in the fifth major release, `goto` needed to be added is not getting better. Nor is one whose maintainers rationalize the choice of backslash as a third, distinct scope resolution operator -- instance-attribute, class-attribute, and now namespace-member.
The sheer number of fails with PHP warrants the 'good language' treatment. The fact that,
08 === 0
Not at all. They mean different things, and they're used for different things. Import-if-it's-available is include, import-or-error-if-missing is require, and they're both quite handy. The once variants do what most programmers would expect, but the non-once ones do what most template users would expect. Should the "once" have been a flag? Yeah, why not? But that doesn't mean the functionality shouldn't even exist.
When the problem is framed thus, most people would recognize that the solution to that problem is a better understanding on the part of the programmer of the flow of control inside his/her application.
The error handing should be done with exceptions. As it is, there are many errors in PHP which are recoverable, but they don't throw exceptions but instead emit other kinds of non-catchable failures. In Python, you would simply `try` to import a module and `catch` a failure to do so, e.g. if that module wasn't installed.
PHP takes it's cues from C -- that's where the idea of include() and require() come from. These functions pre-date the existence of OOP in PHP. There was a time when even the _once() functions didn't exist and you had to manage that yourself.
It's best to think of these functions as low-level building blocks you can use to build on your own abstraction layer. I never call those functions directly.
> The error handing should be done with exceptions.
PHP supports many styles of development. If you prefer errors, you can have those. If you prefer exceptions, you can convert all errors to exceptions with only a few lines of code (there is even a built in exception type for this purpose).
Right, and there's a case for that in languages that need a template library, as well. In some cases, you want to re-render a template for some other place in the output, and in other cases, you'd want to use a previously cached rendered template, and both of those cases are useful.
So, I agree that the distinction between the cases is the result of PHP being both a full programming language and a built-in templating language. I don't view this (in and of itself) as a bad thing, though I would quibble with the exact implementation, which is how it is for historical reasons.
When the problem is framed thus, most people would recognize that the solution to that problem is a better understanding on the part of the programmer of the flow of control inside his/her application.
Since you've already agreed that having the option for rerendering is a feature of including templating as a core feature, it seems like this statement is equivalent to declaring that templating should never be a core feature of a programming language. It's less about the flow of control and more about whether the result is cached. Even programmers who have a good understand of their programs' flow of control occasionally find memoization useful. :)
include/require_once are not statements to the effect of "return same output as the last time I include/required this" but rather "if I haven't already include/required this, do it now."
It's a very difficult proposition to say that good programming requires the latter capability.
So, if you're willing to accept my assertion that Python is a good programming language, then you'll have to agree that that latter capability is the default in at least some good programming languages.
The former capability to which you refer, though, is quite often useful for including template fragments, so I wouldn't want to throw it out, either. If you said, "Hey, these only seem conceptually similar because of the name, and they're really different things", I'd be willing to go with that, I think. Or, if you were to say, "Hey, these are so similar that we shouldn't have a whole separate name for the behavior switch", I'd agree with that, as it's my position. However, it seems as though you're arguing that one of the two behaviors is never needed in a good web application domain language, and I disagree with that.
First, it's important to understand that include/require_once is useful in PHP because of a particular pattern -- include/require the files containing classes and functions I need; these statements are placed at the top of every script that needs those definitions. It's an error in PHP to declare the same function twice (to redeclare). So if you include script A and B, and both depend on C, then you have to use require_once in A and B when they call in C. This way, anyone calling in both A and B won't trigger a redeclaration error.
This use case is not relevant to people using the statements to pull in templates, because you would deliberately place the require statement where you needed it. Someone using the same partial template in the header of a page and in the footer of a page would not care if the template had been invoked before -- "place this in the footer unless you already placed it somewhere else in the document (or even if you simply included it and threw it away, or emailed it to someone, or anything else at all)" would be a very poorly written template.
So what we have is the case that a set of processing scripts all include the same file at the top and this could potentially trigger redeclaration errors. So instead of addressing the fact that the interpreter cannot distinguish a common pattern (multiple inclusion) from something that really isn't even an error (redeclaration), we have four statements that serve very minor variations of the same function.
There are two binary choices here: require or include and once or not once. The distinction between include and require is totally unnecessary -- in what case would you want to optionally include another file, but not even receive notification or change your behavior depending on whether the file was able to be included? The _once distinction is only a guard against redeclaration, and it's beyond me why it matters that something was declared multiple times -- or why the programmer needs to count the number of inclusions.
Ideally, calling in a template would be different from calling in essential definitions, and would be treated differently.
BTW in Python, the import statement is idempotent -- importing multiple times has the same effect as importing once.
I'd say that is the case for any language.
It is like seeing people trying to cure cancer with leeches.
However, it's scary to me that someone is suggesting the potentially fatal-inducing use of "require" over "require_once" (if you call it twice on the same file, you end up re-defining whatever classes or methods were required and the script dies). It seems like optimizing for developer time and simplicity over cpu utilization is better here. Using HipHop would incur a one-time operational cost, but I suspect it would be worth the additional developer and speed gains.
Performance Talk by Rasmus Lerdorf http://vimeo.com/12416792 (skip to 14:30)
require_once: 1579 require: 1318 __autoload: 578
The second test shows a similar result:
require_once: 1689 require: 1382 __autoload: 658
Am I missing something here?
http://stackoverflow.com/questions/186338/why-is-require-onc...
Edit: APC was enabled