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This is a retrospective of the year that has just ended.
In case anybody is still wandering, no, PHP 6 didn’t come out and it will probably not come out any time soon.
Why is it relevant? Since I started this blog, at the end of each year I had a post related to PHP 6 and the fact that it wasn’t released. In 2008 it was a popular question, but nobody is wondering about that anymore, and so I will close this subject now. Let’s return to the year that has just ended.
Close to the middle of the year, the version PHP 5.5 was released, bringing features like: finally , generators and many other enhancements.
Like in 5.4, these are not defining features for the language. In this new version, there are functionalities that can be easily replaced, but if present, they are welcome.
Even though PHP is proving very dynamic lately, I think this year the main keywords were HTML5 and JavaScript.
HTML5 is seeing a lot of improvements and older components begin to have more momentum. The companies are beginning to invest in games that work in the browser using WebGL. Even older games are getting ported to the platform, using technologies like asm.js.
And, because I’ve brought games into the subject, it seems very interesting to me how only 5-7 years ago the games built with JavaScript were relatively simplistic, and now they can be compared with the ones from PCs and consoles.
I think the web revolution, which many were expecting, is taking shape. Finally the Web is a platform in the true meaning and JavaScript a language truly appreciated.
The success is due to all sides, it is not only about ECMA or only about browser manufactures, now it is truly dynamic. The Web revolution is in full blow!
When it comes to backend, the spotlight was on Node.js. It is becoming an important player on the market. New frameworks have appeared and it isn’t a platform mainly used by hackers eager to explore new technologies anymore, but also by large companies, like PayPal, LinkedIn and Yahoo, adding a vote of confidence to it. I think Node.js is finding its place and a niche in the market, and, as a JavaScript fan, I can only be happy.
An advantage of Node.js is that you don’t have to take into consideration different JavaScript versions, like in the browser. It allows the use of the latest features from ECMA freely, an environment where you can develop JavaScript with not headaches.
Technically speaking, it was a very interesting year for web development.
Finally, I want to wish you all an extraordinary 2014!
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The notion of closure in PHP, even though it appeared in PHP 5.3, as I’ve said before on my blog, it was properly done only in 5.4.
Wikipedia tells us:
In computer science, a closure (also lexical closure or function closure) is a function or reference to a function together with a referencing environment—a table storing a reference to each of the non-local variables (also called free variables) of that function.
In PHP this isn’t a very popular concept or very well-known. It is often mistaken for Anonymous Functions. But in functional programming languages it is very popular, because they really need it!
Scheme
When Brendan Eich designed JavaScript, relied on the Scheme language and ended up doing an implementation of this language with a C syntax. The C syntax was and is a lot more popular, and back then (1995) the Java programming language was very “fashionable”.
The Scheme syntax is similar to Lisp, in the sens that is using parenthesis abound expressions in order to execute them. The operators are defined as functions and just like them, there must be placed left of the parenthesis.
Let’s take an Scheme closure example:
1(define (make-counter) 2 (let ((count (begin 3 (display "run parent function and return 0") 4 ))) 5 (lambda () 6 (set! count (+ count 1)) 7 (begin 8 (display "inside child function ") 9 count))))
The function is setting a “count” variable, with the value 0 and displays “run parent function and return 0”, then returns another lambda function, that is incrementing the variable defined in the main function and then displays “inside child function”.
I’m storing the resulting function in a variable in order to later run it multiple times:
1> (define counter (make-counter)) 2run parent function and return 0 3> (counter) 4inside child function 1 5> (counter) 6inside child function 2
In other words, each time I’m calling (make-counter), it will return a new function that has access to the environment at the time at which it was created. If it looks strange because of the syntax, I promise that it will fell a lot more natural in JavaScript.
This concept is very interesting for encapsulation. The environment from the time when the parent function was been executed can be encapsulated, and later it can be used without worrying that it was changed by external causes.
For the functional programming languages this is a very interesting concept. Yet when it comes to object orientated languages, the concept seems almost useless, because objects also have the purpose of encapsulation.
JavaScript
From the beginning JavaScript was a hybrid, a functional programming language, object orientated, with prototype based inheritance. And if this wasn’t enough, the syntax was taken from Java (C).
JavaScript didn’t inherited a lot from Scheme, but it did inherit the closure concept.
A reason why there was a need for closures in Scheme is that that if a function is not finding a variable in its environment, it will search for it in its container’s environment. Let’s take an example:
1(define x 1) 2(define (add-in-env y) (+ x y))
If we call add-in-env with 2:
1(add-in-env 2) -> 3
It looks just as ambiguous as in JavaScript, but is not exactly like that. In Scheme to do mutation is not that easy, simple and transparent, so an subsequent operation of:
1(define x 2)
will result in an error.
In JavaScript resulted a hybrid. Mutation is permitted, but the notion of searching a variable in the current environment remained:
1var x = 1; 2var add_in_env = function (y) { 3 return x + y; 4} 5 6add_in_env(2); // returns 3
Up to this point is ok, but for:
1x = 2; 2add_in_env(2); // returns 4
For this case, things can get out of hand very easy:
But, in order to solve the issue, we can just define a variable in the environment that will finish execution (will close):
1var make_counter = function () { 2 console.log("run parent function and set counter to 0") 3 var count = 0; 4 5 return function () { 6 count = count + 1; 7 console.log("inside child function"); 8 return count; 9 } 10} 11 12var counter = make_counter(); 13console.log(counter()); 14console.log(counter()); 15 16var counter2 = make_counter(); 17console.log(counter2()); 18console.log(counter()); 19console.log(counter2());
The output will be:
1run parent function and set counter to 0 2inside child function 31 4inside child function 52 6run parent function and set counter to 0 7inside child function 81 9inside child function 103 11inside child function 122
Even though the main function finished executing, the environment inside it is kept as a closure for the function that was returned. Only when there aren’t any more references to the sub-function the memory allocated for the closure will also be deallocated.
Even though JavaScript has objects, it doesn’t have private methods. An approach is to add a “_” (underscore) in front of the function name and consider it private. From my point is like asking the developers that will later use the code to consider this function private. Of course this is not very consistent.
Let’s take an example:
1var obj = { 2 _secretFunction : function (key) { console.log(‘do secret ’ + key) }, 3 doStuff : function (key) { this._secretFunction(key) } 4} 5 6obj.doStuff(‘stuff’); // do secret stuff
It seems that there is a public method “doStuff” and a private one “_secretFunction”. Nevertheless you can not prevent a user from calling “_secretFunction” or even worse, to modify it:
1obj._secretFunction = function (key) { console.log('new secret ' + key); } 2 3obj.doStuff('stuff'); // new secret stuff
If we want to hide the function, and make this obvious for everybody, again, we can use closures:
1var obj = (function () { 2 var secretFunction = function (key) { console.log(‘do secret ’ + key) } 3 4 return { 5 doStuff : function (key) { 6 secretFunction(key) 7 } 8 } 9})(); 10 11obj.doStuff(‘stuff’); // do secret stuff
Because the parent function was not stored but rather immediately executed, basically the space in which secretFunction was defined has already finished its execution, encapsulating the logic. The object returned can call the function because it was defined in the same environment as the object.
Looks complicated at first, but is really very easy when you understand the concept.
And then it was… PHP
PHP includes a lot of different options. It was originally developed as a Perl framework, later the engine was rewritten in C.
PHP is a dynamic language that includes a lot of concepts, from objects, interfaces and anonymous functions, up to goto labels. The development direction for the language is not very clear, it rather offers the possibility for different approaches.
In the weird PHP history, somewhere in version 4, syntax for Anonymous Functions was added, but only in PHP 5.3 a more “normal” version appeared.
Also in version 5.3 the first closure version was introduced:
1$scalar = 5; 2 3$closure = function () use ($scalar) { 4 return 'Scalar: ' . $scalar . PHP_EOL; 5}; 6 7echo $closure(); // Scalar: 5 8 9$scalar = 7; 10 11echo $closure(); // Scalar: 5
This version mostly worked, but you had to specify what you want to send to the closure.
And there were other inconveniences:
1<?php 2class Foo { 3 private function privateMethod() { 4 return 'Inside private method'; 5 } 6 7 public function bar() { 8 $obj = $this; 9 return function () use ($obj) { 10 return $obj->privateMethod(); 11 }; 12 } 13} 14 15$obj = new Foo(); 16$closure = $obj->bar(); 17echo $closure(); 18 19Fatal error: Call to private method Foo::privateMethod() from context '' in [...][...] on line 10
Is not working because you can not send $this as a parameter to a closure, and if you try the above trick you still can’t access the private methods. Remember, this was happening in PHP 5.3.
The idea to introduce a closure of this kind seems strange to me. But this is not the first time something “strange” is introduced in PHP, as I was saying before about the Anonymous Functions. Sometimes is looking like work in progress.
I think everybody was expecting a more JavaScript like closures. I think that JavaScript had a big influence in making this concept so popular.
In version PHP 5.4 things changed, we finally have a closure as we would expect:
1class Foo { 2 private function privateMethod() { 3 return 'Inside private method'; 4 } 5 6 public function bar() { 7 return function () { 8 return $this->privateMethod(); 9 }; 10 } 11} 12 13$obj = new Foo(); 14$closure = $obj->bar(); 15echo $closure(); // Inside private method
And it works!
You can even do:
1unset($obj); 2echo $closure();
and it will work, because the object in which the closure was defined remains in memory until either the script finishes execution, or a call like this is made:
1unset($closure);
For more details on how closures work in PHP 5.4, check out this post.
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PHP 5.4 was released!
Even though is already yesterday news… literally, yesterday 1 March was released.
The complete list of changes is available on php.net.
I’m sorry that we still don’t have scalar type hinting in this version. The only change to type hinting was the “callable” word was added, about which I’ve talked in the closure in PHP 5.4 blog.
Another interesting thing is that this time register_globals and magic_quotes_gpc were really removed, so the old PHP 4 apps don’t get to be compatible anymore with the help of a couple of flags in php.ini.
Also the hex2bin() function was added, of course is not that important, but is interesting that the bin2hex() function existed since PHP 4. 🙂
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The concept of closure was introduced in PHP 5.3, with the new “more traditional” syntax for anonymous functions.
PHP 5.3
In PHP 5.3, a closure will rely on the term “use”, which was passing the variables to the anonymous function, making it a closure.
The problem is that the anonymous function will only be able to access the variables that have been passed with “use”. When it comes to objects, there are passed by reference by default, but scalar variables (int, string, etc.) are passed by value, as this is the default behavior in PHP 5+:
1$scalar = 5; 2 3$closure = function () use ($scalar) { 4 return 'Scalar: ' . $scalar . PHP_EOL; 5}; 6 7echo $closure(); // Scalar: 5 8 9$scalar = 7; 10 11echo $closure(); // Scalar: 5
Another problem is that you cannot pass $this when the anonymous function is declared inside an object, so only the public method and properties can be accessed inside the closure.
PHP 5.4
In PHP 5.4 the keyword “use” is optional, and the entire environment where the function was created is available inside the function.
The advantage is that when the anonymous function is created inside another function or method, the anonymous function has access to the environment where it was created, even after the execution of the environment is over. The objects from this environment will be unset, only after the last reference to the closure will be unset:
1class testClass { 2 3 private $changeableVar = 1; 4 private $bigVar; 5 6 public function __construct() { 7 // Allocate a big variable so we can see the changes in memory 8 $this->bigVar = str_repeat("BigWord", 5000); 9 } 10 11 /** 12 * A method that returns the closure 13 */ 14 public function closure() { 15 16 return function () { 17 // Display the value of a private property of the object 18 echo 'Private property: ' . $this->changeableVar.PHP_EOL; 19 20 // Change the value of a private property of the object 21 $this->changeableVar = 2; 22 }; 23 } 24 25 /** 26 * Method that displays a private property 27 */ 28 public function showChangeableVar() { 29 echo 'Private property in method: ' . $this->changeableVar.PHP_EOL; 30 } 31 32} 33 34// Memory befor the objects is created 35echo "Memory: " . memory_get_usage() . PHP_EOL; // Memory: 229896 36 37// Create object 38$testObj = new testClass(); 39 40// Create closure 41$closure = $testObj->closure(); 42 43// Execute closure 44$closure(); // Private property: 1 45 46// Displaying the current value of the private property 47$testObj->showChangeableVar(); // Private property in method: 2 48 49// Memory befor object will be unset 50echo "Memory: ". memory_get_usage() . PHP_EOL; // Memory: 266240 51 52// Unset the object 53unset($testObj); 54 55// Memory after the object was distroyed, there is no big difference in memory 56echo "Memory: ". memory_get_usage() . PHP_EOL; // Memory: 266152 57 58// Run closure after the object in which it was created was unset 59echo $closure(); // Private property: 2 60 61// Unset closure and with it the object environment 62unset($closure); 63 64// Memotry after the las reference to the object (closure) is unset 65echo "Memory: " . memory_get_usage() . PHP_EOL; // Memory: 230416
Callable type hinting
Another new feature introduced in PHP 5.4 regarding closures is the new “type hint”: “callable”. Actually callable is referring to any anonymous function, and even to a new way of calling a method of an object:
1<?php 2 3// A function that uses type hinting 4function typeHinting(callable $a) { 5 echo $a() . PHP_EOL; 6} 7 8// A closure 9$closure = function () { 10 return __FUNCTION__; 11}; 12 13// Call the type hinting function with the closure 14typeHinting($closure); // {closure} 15 16class testClass { 17 public function testMethod() { 18 return __METHOD__; 19 } 20} 21 22// A mock object 23$testObj = new testClass(); 24 25// The new way of calling object methods 26$objCallable = array($testObj, 'testMethod'); 27 28// Call type hinting function with the new method calling way 29typeHinting($objCallable); // testClass::testMethod
I believe that only now we can really say that PHP supports closures, the right way!
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It became a tradition for me to begin my annual review on this subject.
PHP 6 is as close to be released as it was last year, or two years ago, which is without perspective. This year PHP 5.4 reached RC4 and a final version will probably be released soon, this means that work on PHP 6 will not be resumed soon. But more about PHP 5.4 with another occasion, is on my “TODO” list to see what got into RC4.
As the main keyword for me in PHP 5.3 were namespaces, Anonymous functions, closures and garbage collector, in PHP 5.4 it seems that those keywords are going to be traits, the new closures and scalar type hinting, next to many other new features.
When I’ve wrote my first annual review blog about PHP 6, I was mainly working on Romanian websites, hence my desire for a version that will natively support this language and any other without any changes. Back then I was mainly working directly with the language, without using a framework most of the time. But since then a lot of time has passed and many things have changed, now I’m using almost exclusively frameworks and other platforms that are taking me further away from the language, offering me a different architectural perspective.
After more then an year with NCH, I’ve decided that is time for a change. This is also a company from the states with a branch in Romania, and this time is Optaros. Although I wasn’t trying to change my work place, I’ve responded to an invitation to an interview, and long story short, I left. For a long time I’ve wanted to work again for external clients, after working at NCH where all the projects were internal, I’ve wanted a change.
Again the projects are even bigger, with other scalability issues. But I think that makes web development so interesting, the bigger the scalability issues, the bigger the project.
Last year the main keywords were Linux si Symfony framework. For this year that is just ending the main keywords probably were: Magento and Drupal.
After a short period of working with Magento, I can say that it seems incredible how a platform so big has so little documentation and a lot of the time so inconsistent. It is a very complex platform and a lot of things can be done with it, but when it comes to documentation, it seems like the usual approach is to just analyze the core. Coming from the Symfony world, where there are literary books for documentation, available for free, it seems incredible how little and disorganized is the Magento documentation. But this is also a subject for another blog. A think that the Optaros team played an important role in helping me understand how to approach the issues.
Another major event for me this year was the Yahoo! Open Hack Day, event that this year was also held in Romania. I don’t think I’ve ever seen so much enthusiasm and energy in a single place, in a single day. For me as a developer it was an unforgettable experience, one of those moments that remind me why I’ve chosen this profession.
Also this year I’ve passed my PHP 5.3 certification exam, at the beginning of the year. The exam wasn’t as difficult as I’ve expected, even though the tension remains the same. The fact that it wasn’t my first certification exam helped, it’s incredible how much you remember when you start the reading the documentation again. Last year I’ve decided that I have to take at least an certification exam every year, so I have to get started on preparing for the next one.
As a conclusion, 2011 was a good year, full of challenges and accomplishments, even though I haven’t checked a lot of entries on my last year’s resolution, I’ve done quite a few that were not on that list. But now is time for another new year’s resolution.
And now I wish you an 2012 full of achievements! Happy new year!