Looking for more information on how to do PHP the right way? Check out PHP: The Right Way

Freek Lijten:
Value objects
Jul 16, 2015 @ 10:17:14

Freek Lijten has written up a post looking at value objects, how he feels they're not used enough in modern development and a few practical applications of them in action.

I would like to talk about value objects for a bit. Value objects are very underused, very powerful and general good stuff. They might not change your world but they will change, very subtle, a lot of the code you write. I hope to give the shortest possible introduction to the concept and follow up with a couple of example that make me like value objects so much.

He briefly introduces some of the basics of value objects including one of the main points: their immutability. He gives an example of working with a "10 Euro" object, pointing out that once an operation is performed using it, it becomes a different object not just one with a value changed. He also illustrates with an email address example pointing out that email addresses themselves (not the relation to the user) almost never change. He ends the post with another interesting value object scenario using IDs and making them type hint-able.

tagged: value object

Link: http://www.freeklijten.nl/home/2015/07/16/Value-objects

Julien Pauli:
PHP closures
Jul 10, 2015 @ 10:54:29

Julien Pauli has posted a look at PHP's closures and how they're actually handled internal to the language.

Back in 2009, when PHP 5.3 got released, a new feature (among many others) were introduced : anonymous functions (also called lambdas or closures). The feature was very expected, as closures have proved their utility through several other languages, particularly javascript that web developers master. [...] Let's see together how Closures have been added to PHP, as usual by turning to the truth : the PHP source code.

He starts at the beginning (a good place to start) and talks about the work that needed to be done on the internals before closures could even be introduced. He walks through the changes made to object handling to make them "callable" and the addition of the "zend_closure" object type. He then gets to the part where "the magic happens" and shows how the userland closure is translated and executed. He ends the post with a look at two other topics: scoping with "$this" and the special handling that was needed for reflection and direct calls to "__invoke".

tagged: closure language functionality object callable scope reflection invoke

Link: http://jpauli.github.io/2015/07/08/php-closures.html

Davey Shafik:
Class Constants, How Do They Work? (Or: You Learn Something New Every Day...)
Jul 09, 2015 @ 08:24:43

Davey Shafik has posted a quick article to his site talking about class constants and something new he learned about them (and how it relates to the uniform variable syntax handling in PHP7).

Yesterday on Twitter there was a conversation started by Marco Pivetta regarding a particularly horrible bit of code he had spotted [that] creates a string using sprintf() by prefixing ::PARAMNAME with the result of calling get_class() on the $api variable, and then passes that string into constant() which will give you the value of a constant using it’s string name.

The conversation continued with comments from Elizabeth Smith about why this workaround was needed in the past. Davey also suggests that it won't work as expected if the input is an object and not a string but a test from Trevor Suarez proved that incorrect as well (it does work). He ends the post talking about PHP7 and showing how, thanks to the uniform variable syntax changes, this same kind of handling can be done in many other ways too.

tagged: class constant php7 uniform variable synatx getclass object string

Link: http://daveyshafik.com/archives/69193-class-constants-how-do-they-work-or-you-learn-something-new-every-day.html

Paul Jones:
A Factory Should Create, Not Retain
Jul 08, 2015 @ 08:45:31

Paul Jones has posted his thoughts about factory behavior in PHP applications (well, really any kind of application as it's a pan-language concept). He suggests that factories should only create the objects requested and not persist them.

In a recent Reddit conversation, some of us went off on a tangent about factories. I maintained then, and do now, that a “factory” always-and-only returns a new instance. If you have a “factory” that returns anything other than a new instance, it’s not a factory alone. In the case of factory methods, it is a factory + accessor; in the case of factory objects, it is a factory + registry. A “factory” (whether a factory method or factory object) is one way to separate object creation from object use.

He gives an example of a case where an object needs to be created for a "doSomething" method. His first example shows the creation of the "Item" inline, mixing the creation and use of the object into the same place. He replaces this with a "factory" class/method that only returns the new "Item" requested. He points out that a factory method that retains the object (like as a class property) has the same problem as the first example - retention. Instead he suggests an intermediate "collaborator" that splits out the creation and retention once again.

tagged: factory retain create object method collaborator example

Link: http://paul-m-jones.com/archives/6161

Paul Jones:
Modernizing Serialized PHP Objects with class_alias()
Jul 01, 2015 @ 09:57:50

Paul Jones has posted an article to his site with another helpful hint to modernize your legacy PHP application. In the post he looks at updating serialized object handling with the help of the class_alias function.

Several weeks ago, a correspondent presented a legacy situation that I’ve never had to deal with. He was working his way through Modernizing Legacy Applications in PHP, and realized the codebase was storing serialized PHP objects in a database. He couldn’t refactor the class names without seriously breaking the application. [...] Before I was able to reply, my correspondent ended up changing the serialization strategy to use JSON, which was a rather large change. It ended up well, but it turns out there is a less intrusive solution: class_alias().

He talks about how this function could be useful to prevent the need for updating the class name in every serialized instance by setting up an alias to the new name. You can even use namespacing in the alias that will let the autoloader work with the PSR-0/PSR-4 handling to correctly load the class. With this in place, you can then refactor to the new version of the class without worry of breakage.

tagged: modernize serialized object classalias namespace psr0 psr4

Link: http://paul-m-jones.com/archives/6158

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

Jonathan Wage:
Using the Symfony Expression Language for a Reward Rules Engine
May 28, 2015 @ 10:07:27

Jonathan Wage has a new tutorial on his site showing you how to use the Symfony Expression Language to create simple logic statements. He illustrates with a project they (OpenSky) applied it on - a "reward" rules engine.

We recently adopted the Symfony Expression Language in the rules engine at OpenSky. It has brought a new level of flexibility to our system and creating new logic has never been easier. [...] The expression language allows you to perform expressions that get evaluated with raw PHP code and return a single value. It can be any type of value and is not limited to boolean values.

He starts with a simple example, showing how it can return a boolean based on the results of an evaluation of an array of data. He then takes this up to the next level and use it with a Doctrine object, evaluating the results of methods to apply "rewards" to a user's account. He shows how to define the Doctrine objects with the necessary methods, how to write the rule and a lookup class to find rules that apply to the current situation.

tagged: symfony expression language rules engine tutorial doctrine object

Link: http://jwage.com/post/76799775984/using-the-symfony-expression-language-for-a-reward

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/

Julien Pauli:
Zoom on PHP objects and classes
Mar 26, 2015 @ 12:50:49

Julien Pauli has a recent post to his site that "zooms in" on objects and classes with a look behind the scenes at how they're handled in the PHP source (at the C level) with plenty of code examples and explanations as to how they work.

Everybody uses objects nowadays. Something that was not that easy to bet on when PHP5 got released 10 years ago (2005). I still remember this day, I wasn't involved in internals code yet, so I didn't know much things about how all this big machine could work. But I had to note at this time, when using this new release of the language, that jumps had been made compared to old PHP4. The major point advanced for PHP5 adoption was : "it has a new very powerful object model". That wasn't lies. [...] Here, I will show you as usual how all this stuff works internally. The goal is always the same : you understand and master what happens in the low level, to make a better usage of the language everyday.

The article does a great (if lengthy) job of covering everything that happens with PHP's objects and class system, including stats about memory consumption. He includes both the PHP code and the C code to illustrate what's happening with classes, interfaces, traits and object methods/attributes (including object references). He also talks about what "$this" is and how class destructors are handled.

tagged: object class behindthescenes detail c code memory usage

Link: http://jpauli.github.io/2015/03/24/zoom-on-php-objects.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