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Nikita Popov:
Internal value representation in PHP 7 - Part 2
Jun 22, 2015 @ 10:45:41

Nikita Popov has posted the second part of a series looking at how PHP 7 represents values internally. In the first part of the series the focus was on the major change from PHP 5: the zval updates and how they're allocated. This new post gets into more of the details on each of the types and how they're handled.

In the first part of this article, high level changes in the internal value representation between PHP 5 and PHP 7 were discussed. As a reminder, the main difference was that zvals are no longer individually allocated and don’t store a reference count themselves. Simple values like integers or floats can be stored directly in a zval, while complex values are represented using a pointer to a separate structure.

[...] In the following the details of the individual complex types will be discussed and compared to the previous implementation in PHP 5. One of the complex types are references, which were already covered in the previous part. Another type that will not be covered here are resources, because I don’t consider them to be interesting.

He goes through a few of the different types including strings and arrays and then gets into detail on how objects have changed from PHP 5 to PHP7. He also talks about "indirect zvals" (the IS_INDIRECT handling) that points to another zval instance rather than embedding it. Finally, he talks about two other constants, IS_CONSTANT and IN_CONSTANT_AST, and how they're used behind the scenes with some example code to illustrate.

tagged: internal value variable representation php7 zval types string array object constant ast

Link: http://nikic.github.io/2015/06/19/Internal-value-representation-in-PHP-7-part-2.html

Evert Pot:
PHP's callable typehint too loose?
May 07, 2015 @ 10:19:56

In his latest post Evert Pot wonders if the current implementation of the "Callable" type in PHP is too loose when it comes to what it will accept as a valid callable resource.

PHP got support for closures in version 5.3, and in PHP 5.4 we got support for a callable typehint. [...] All these little changes make it feel more comfortable to apply functional programming concepts to PHP, but occasionally we need to drop back to using less aesthetically pleasing code.

In his examples of "less aesthetically pleasing code" he shows a few different methods that work that aren't the typical closure or object arguments (like passing in an array of object+method name). He also shows an interesting option where you can use a string with a static method call (ex: "MyClass::method") and it will still be accepted. He points out that for this to work correctly in all situations, the call_user_func method should be used, not just calling the input directly.

tagged: callable typehint loose object method array variable iscallable calluserfunc

Link: http://evertpot.com/on-callables-and-closures/

Theo Kouzelis:
Improving Readability of PHPUnit Data Providers
Apr 10, 2015 @ 12:01:28

Theo Kouzelis has a recent tutorial posted showing you how to make your PHPUnit tests a bit cleaner with the help of data providers, a built-in tool for PHPUnit that allows for easier validation of larger datasets.

When writing tests I try to describe the test in the function name. I use the format testDoesSomethingWhenPassedSomething to first describe the assertion and then the context. [...] When I have many data sets running against the same test I will use the frameworks data providers to make the code less verbose.

He includes code examples to show both the difference between the single data tests and one using a set of email addresses to validate their correctness. He notes that the error message using data providers can be confusing (and maybe hide the real problem) so he offers a solution to make it more readable: associative arrays. The trick is that PHPUnit uses the key to display the error and by making this unique you can make the error output more informative.

tagged: dataprovider tutorial readability phpunit unittest associative array

Link: http://theo.codes/php/improving-readability-of-phpunit-data-providers.html

Derick Rethans:
Xdebug 2.3: Enhanced xdebug_debug_zval()
Mar 03, 2015 @ 10:50:41

Derick Rethans has posted another article about Xdebug and some of the changes made in the most recent release, version 2.3. In his previous post he talked about the improvements to var_dump and in this one he shares updates to the xdebug_debug_zval handling.

xdebug_debug_zval() has been around for quite some time, to provide correct information about how PHP internally stores a variable. Unlike PHP's built in debug_zval_dump() function, it does not modify the variable information that it tries to show. This is because instead of passing in a variable, you pass in its name. Passing a variable into a function, can modify the various parameters that are associated with this variable, such as the is_ref and refcount fields.

He includes a bit of background about what the function is used for and then shows the difference it has in 2.3: the ability to handle nested data structures including property dereference support. He includes a few code examples showing the use of the function and the output it would generate for both an array and an object.

tagged: xdebug enhanced xdebugdebugzval array subarray object dereference

Link: http://derickrethans.nl/xdebug-2.3-xdebug-debug-zval.html

Nikita Popov:
PHP's new hashtable implementation
Dec 26, 2014 @ 10:20:10

In his latest post Nikita Popov gives a detailed look at PHP's new hashtable implementation and what kinds of improvements it offers over the previous methods. The "hashtable" handling is how the language references array values created during the execution of a script.

About three years ago I wrote an article analyzing the memory usage of arrays in PHP 5. As part of the work on the upcoming PHP 7, large parts of the Zend Engine have been rewritten with a focus on smaller data structures requiring fewer allocations. In this article I will provide an overview of the new hashtable implementation and show why it is more efficient than the previous implementation.

He starts with an introduction to the concept of hashtables, describing them as "ordered dictionaries" of key/value pairs that (internally) reference values in an array. He looks at the old method PHP used to make these links and how the new version, with the help of zval handling, is different. He talks about how it handles the order of elements, does lookups and the introduction of "packed" and "empty" hashtables. He ends the post with a look at this new implementation's memory utilization and what kind of performance gains we can expect with its introduction in PHP7.

tagged: hashtable array implementation php7 performance memory lookup

Link: http://nikic.github.io/2014/12/22/PHPs-new-hashtable-implementation.html

Stanislav Malyshev:
Objects as keys
Dec 15, 2014 @ 09:18:50

In his latest post Stanislav Malyshev looks at a RFC he's proposed to allow array keys to be objects including some of his thoughts behind the proposal and how he sees it being helpful to the language.

I’m going to put to vote soon another of my RFCs, namely one about “objects as keys“. So, I want to outline the case for it here and address some criticisms and questions raised while discussing it.

He starts off by answering the "why" question, mentioning specially the introduction of things like GMP numbers and how, despite them seeming to work like numbers, other things can be done with them. He talks about how you'd use this functionality "the right way" and how that'd relate back to value objects. He answers a few other questions about the proposal including why it's better than just using __toString or spl_object_hash instead. He spends the rest of the post looking at some of the implementation problems, disadvantages and some of the possible names (function names) for the handling.

tagged: object array key rfc proposal gmp number

Link: http://php100.wordpress.com/2014/12/14/objects-as-keys/

Michael Dowling:
Favor Hash Lookups Over Array Searches
Mar 21, 2014 @ 10:47:34

Michael Dowling has a recent post to his site comparing the performance of hash lookups versus array searches.

A common programming requirement is to match a string against a set of known strings. For example, let’s say you were iterating over the words in a forum post and testing to see if a word is in a list of prohibited words. A common approach to this problem is to create an array of the known prohibited words and then use PHP’s in_array() function to test if the string is found in the list. However, there’s a simple optimization you can make to significantly improve the performance of the algorithm.

He includes two pieces of sample code - one showing the searching of an array using in_array and the other running an isset to locate a key. He points out that the in_array method is quite a bit slower than the hash (key) lookup and includes a benchmark script to prove it.The results are pretty clear, with the hash lookup coming in about 480% faster than the in_array. He also points out that as the size of the strings you're comparing grows, the performance of in_array drops even more.

tagged: hash lookup search array inarray benchmark

Link: http://mtdowling.com/blog/2014/03/17/hash-lookups-over-array-search/

Nikita Popov:
The case against the ifsetor function
Jan 13, 2014 @ 09:22:52

In his latest post Nikita Popov aims to make a case against the introduction of the "ifsetor" function to be introduced into the PHP language. This function takes in a variable to find and, if found returns it. If not, it doesn't produce an error (or warning).

Recently igorw wrote a blog post on how to traverse nested array structures with potentially non-existing keys without throwing notices. The current “idiomatic” way to do something like this, is to use isset() together with a ternary operator. [...] Someone on /r/PHP pointed out that there is an alternative approach to this problem, namely the use of an ifsetor function.

He goes on to talk about by-reference argument passing, why requesting an undefined array index doesn't really throw an error and how writes don't have the same issues as reads. He then gets into his own issues around the "ifsetor" function, namely:

  • Creation of dummy values
  • No notices for nested indices
  • Null values treated as non-existing
  • Default is always evaluated
  • By-reference passing often forces a copy

He summarizes most of the issues in one statement - "there is way too much by-ref magic involved". He then looks at some of the ways that this could be helped but opts instead for something more like "get_in" as proposed by Igor.

tagged: ifsetor getin array read write problem byreference

Link: http://nikic.github.io/2014/01/10/The-case-against-the-ifsetor-function.html

SitePoint PHP Blog:
Fun with Array Interfaces
Dec 09, 2013 @ 10:53:06

On the SitePoint PHP Blog a tutorial has been posted recently about having some fun with array interfaces via some of the functionality provided through the SPL (Standard PHP Library).

As a programmer who works with different languages every day, I find a lot of joy in learning how things are done differently in other languages and seeing if I can do the same in PHP. One thing I liked in particular in Python was how one can emulate features of native data types in custom classes. [...] I thought it would be nice if you could do the same in PHP on an instance of your custom classes and not only arrays. PHP lets us do this with array interfaces.

He illustrates his intent with some basic Python functionality and shows how to use various PHP interfaces to achieve a similar functionality. He talks about SPL interfaces like Countable, ArrayAccess and Iterator to make objects more useful in an array handling environment. His example uses the idea of a set of user's tweets (from Twitter) and shows the implementation of these three interfaces.

tagged: array interface countable arrayaccess iterator tutorial

Link: http://www.sitepoint.com/fun-array-interfaces

Array Manipulation in PHP, the Correct Way
Nov 08, 2013 @ 10:08:04

On the Leve.rs blog there's a recent post showing what they consider is the right way to work with arrays in PHP. It shows three things you can do to use PHP's own functionality to more correctly perform some common array operations.

More often than not, when PHP developers debug others’ code, the majority of each method is taken up by array manipulations. Spending this much time on array manipulations is a huge hassle when trying to understand any given method. In order to speed up the debugging process, it’s important to start writing array manipulations the correct way, first. Here are a few examples of code I have either written myself or had to fix in the past. It is time every PHP developer knows how to manipulate arrays properly!

Their three tips relate to:

  • Merging Arrays
  • Array Value Manipulation (with array_walk)
  • Array Value Manipulation (append with the plus sign, "+")
tagged: array manipulation correct merge value walk plus

Link: http://leve.rs/blog/correct-array-manipulation-in-php/