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Jesse Schutt:
Simplifying Conditional Expressions
Apr 04, 2016 @ 14:47:43

Jesse Schutt has posted a set of helpful hints around simplifying conditional expressions in your PHP code. This can not only make them more readable but also easier to maintain in the future.

As I’ve been reading through Refactoring by Martin Fowler, I’ve found it helpful to rewrite some of the examples from the book in PHP in order to cement the concepts into my mind. While Martin’s examples are primarily in Java, I’ve found an overwhelming majority of the concepts apply to PHP, which is where I spend most of my programming time.

In today’s article, I will attempt to rework the Simplifying Conditional Expressions (pp. 237-270) section into a handful of PHP-based examples.

He touches n a few different types of conditional refactoring and provides examples for each:

  • Decomposing the Conditional
  • Consolidate Conditional Expression
  • Consolidate Duplicate Conditional Fragment
  • Replace Nested Conditional with Guard Clause

He ends the post with a reminder about why refactoring like this is important to both you and your code:

Computers excel at taking sets of instructions and stepping through them systematically. They don’t need code to have informative method or variable names. They don’t even need the code to be formatted in a specific pattern (aside for the syntactical requirements). Our goal in simplifying conditional expressions should be to make the code read easier for humans, not for computers.
tagged: simplify conditional expression example refactor tutorial

Link: http://zaengle.com/blog/simplifying-conditional-expressions

Symfony Finland:
It's time to get creative with the Symfony Expression Language
Mar 21, 2016 @ 10:39:23

On the Symfony Finland site there's a post encouraging you to "get expressive" with the Symfony Expression Language. The Symfony Expression Language is a part of a component in the Symfony framework that allows for custom evaluation and action in the form of a specially formatted string.

Way back in November 2014 the Symfony team introduced the ExpressionLanguage component. It is essentially a simplified version of control structures that you use in the Twig templating language, producing a single value in the end.

The feature has a number of uses, but seems to be under utilized by the Symfony and PHP communities - especially in higher level functionalities. [...] I think there is a lot of room for developers to adopt the component in many different functionalities, not only for routing, access control and so on.

The post goes on to talk about expression languages in general and how they're present in other languages too (like Java with JUEL). He then shares a basic example evaluating the data in an array and getting back a pass/fail result.

tagged: symfony expression language tutorial introduction juel java

Link: https://www.symfony.fi/entry/its-time-to-get-creative-with-the-symfony-expression-language

Joe Watkins:
Hacking PHP 7
Mar 16, 2016 @ 10:16:38

In this post to his site PHP (core) developer Joe Watkins talks about "hacking PHP 7" based on two screencasts he's made on the subject.

Writing extensions is fun, but it's not as fun as hacking PHP. So, we're going to focus on hacking, we're going to imagine that we are introducing some new language feature, by RFC.

Without focusing on the RFC process itself, you need to know which are the relevant parts of PHP you need to change, in order to introduce new language features. You also need to know how PHP 7 works, about each stage of turning text into Zend opcodes.

After talking a bit about some of his thoughts and troubles with screencasting in general he looks at "The Beginning" of PHP's translation from text to functionality: the lexing. He introduces the basic concept around how a lexer works and how it migrates the pieces over to tokens. He then starts in on the parsing of these tokens and, finally, the AST (abstract syntax tree) resulting from the combination of these pieces, executed against a piece of code.

With that out of the way, he starts in about the "hack" - a hipster expression that only works with strings and throws an exception otherwise. He shows the pieces he had to edit to create this new expression and it's matching token/AST node.

tagged: php7 hack lexer parser ast tree hipster expression screencast

Link: http://blog.krakjoe.ninja/2016/03/hacking-php-7.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

Marc Morera:
Defeating Expression Language
May 18, 2015 @ 08:38:27

Marc Morera has a new post to his site wanting to help you defeat Symfony's expression language and perform the same functionality, just more on the code side (another option).

How beautiful Expression Language definitions are, right? I mean, inserting that complex expressions in a Dependency Injection configuration file is so nice and fast if you need to inject the result of a method in a service (one of the multiple examples we can see). [...] This is not a bad idea, really, but because we are engineers and we should have as much information as possible in order to be able to choose between the best option, always, I will show you another way of defining this piece of code.

He shows how to write some code using the Factory design pattern structure to reproduce a bit more complex piece of expression language. He shows the setup of the services.yml file to define the "managers" and classes/services to be injected. He also notes that this removes the need for the "symfony/expression-language" dependency and makes things more portable in the future.

tagged: expression language symfony alternative factory dependencyinjection services configuration

Link: http://mmoreram.com/blog/2015/05/18/defeating-expression-language/

Knp University:
Symfony Service Expressions: Do things you thought Impossible
May 06, 2015 @ 12:50:13

The Knp University site there's a new post showing you an interesting thing you can do with Symfony2 service definitions - use more complex expressions to load and supply service dependencies.

[Using] the @= means that you’re using Symfony’s Expression Language, which let’s you mix dynamic logically into your normally-static service definitions. Normally, if you want to inject a repository, you need to register it as a service first, using a factory. And while that’s fine (and probably better if you’re injecting the factory a lot), using the expression language is well, kinda cool.

They include an example of the compiled container code that would be produced from the example expression. They also show how to use the same expression language to read configuration information and pass it in as an argument to the created service. The show the pull of a configuration setting "email_from_username" and how to inject it via the expression language.

tagged: service expression language tutorial introduction configuration example

Link: http://knpuniversity.com/blog/service-expressions

Nikita Popov's Blog:
The true power of regular expressions
Jun 15, 2012 @ 08:42:57

Nikita Popov has a new (language agnostic) post to his blog today about one of the most powerful things you can use in your development - something that a lot of developers don't understand the true power of - regular expressions.

As someone who frequents the PHP tag on StackOverflow I pretty often see questions about how to parse some particular aspect of HTML using regular expressions. A common reply to such a question is: "You cannot parse HTML with regular expressions, because HTML isn’t regular. Use an XML parser instead." This statement - in the context of the question - is somewhere between very misleading and outright wrong. What I’ll try to demonstrate in this article is how powerful modern regular expressions really are.

He starts with the basics, defining the "regular" part of "regular expression" (hint: it has to do with predictability) and the grammar of the expressions. He talks about the Chomsky hierarchy and how it relates to the "regular" as well as a more complex mapping of expression to language rules. He talks about matching context-free and context-sensitive languages and unrestricted grammars as well.

tagged: power regular expression define theory context


Sankuru Blog:
A simple bytecode compiler with virtual machine, written in Php, for the EL language
Dec 30, 2011 @ 11:06:36

On the Sankuru blog there's a recent post looking at the construction of a simple bytecode compiler with a virtual machine as written in PHP (for Expression Language).

In my previous blog posts, I demonstrated how we can use the builtin PCRE library, to create a lexer in Php. I also showed how to use Bison-generated LALR1 parser tables in Php. In this blog post, I will re-use these lexing and parsing facilities to compile EL programs from within Php.

He uses his lexer/parser (available for download) in an example program that outputs some values and does some simple mathematical operations. There's sections detailing the Bison grammar used, execution stacks, callbacks and the bytecode it produces.

tagged: bytecode compiler virtual machine expression language


Practicing Regular Expressions with Search and Replace
Nov 23, 2011 @ 14:27:59

On PHPMaster.com today there's a new tutorial that shares a few regular expression tips about doing some search and replace in your content.

So how can you practice using regex if you are limited to just using them in your code? The answer is to use a utility, of which there are many, that uses regex for performing search and replace. I’m sure everyone is familiar with the standard “find x and replace it with y” type of search and replace. Most IDEs and text editors have built in regex engines to handle search and replace. In this article I’d like to walk through a series of exercises to help you practice using regex.

His examples are based on Netbeans but can be used in just about any IDE that supports regex (or even just your code). He shows how to match word boundaries, do some grouping, work with back references and doing some search/replace based on multiple groupings.

tagged: regular expression practice search replace boundaries group backreference


Johannes Schmitt's Blog:
A New Killer Feature for Symfony2 Security
Oct 31, 2011 @ 14:26:08

Johannes Schmitt has a new post about his "killer feature" he's added to the security for Symfony2 framework (as a bundle) - a new customized expression-based query language that's compiled down to native PHP to make permissions checking simpler and faster.

If you have used the Symfony2 Security Component to any modest degree, you will know that we have a quite heavy voting system which uses attributes like "IS_AUTHENTICATED_FULLY" to make authorization decisions. [...] If you are concerned about performance, then you should not be all too generous with the isGranted() calls. The second option would work as well, but writing a new voter each time you need to make a new check does not really seem ideal either. Fortunately, we can do better.

He includes an example of this expression language in a direct isGranted() call, a string that checks to see if a user has three different roles, and a snippet showing the same thing in the docblock comment of a controller method. The second is a bit more complex, checking for an admin role or if the user is the one that should be deleted. You can find more doucmentation here.

tagged: symfony2 framework security bundle expression language allow deny