larry@garfieldtech.comWhen I started writing PHP... (13.2.2019, 01:46 UTC)
When I started writing PHP...

I don't know exactly when I started writing PHP. It was shortly after the start of my second quarter of my freshman year of college, when a newly-met friend of mine introduced me to PHP as an easier to understand alternative to Perl. That puts it, I think, somewhere in January or February of 1999.

20 years ago, give or take a week. I have been writing PHP for two decades. That's more than half my lifetime. I feel old.

I thought it would be amusing (mostly at my expense) to look back a bit on just how much the PHP world has changed in the last two decades.

Larry 12 February 2019 - 7:46pm
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Evert Pot411 Length Required (12.2.2019, 15:00 UTC)

Most HTTP requests that have a request body, will also have a Content-Length header indicating how big the body will be. However, this is optional for some cases, such as when Chunked Transfer Coding is used.

It’s useful for a client to not include a Content-Length header for a few different cases. For instance, a client might send a HTTP request body based on a stream.

If a server does not support this feature, it can indicate this by sending back 411 Length Required.

In a situation like this, a recourse a client might have is to buffer the entire request to determine the real length.

Example

HTTP/1.1 411 Length Required
Content-Type: text/html
Server: curveball/0.6.0

<h1>This server requires a Content-Length</h1>

References

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thePHP.ccHelp! My tests stopped working. (12.2.2019, 07:00 UTC)
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PHP: Hypertext PreprocessorPHP 7.3.2 Release Announcement (7.2.2019, 00:00 UTC)
The PHP development team announces the immediate availability of PHP 7.3.2. This is a bugfix release, with several bug fixes included.All PHP 7.3 users are encouraged to upgrade to this version.For source downloads of PHP 7.3.2 please visit our downloads page, Windows source and binaries can be found on windows.php.net/download/. The list of changes is recorded in the ChangeLog.
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PHP: Hypertext PreprocessorPHP 7.2.15 Released (7.2.2019, 00:00 UTC)
The PHP development team announces the immediate availability of PHP 7.2.15. This is a bugfix release.All PHP 7.2 users are encouraged to upgrade to this version.For source downloads of PHP 7.2.15 please visit our downloads page, Windows source and binaries can be found on windows.php.net/download/. The list of changes is recorded in the ChangeLog.
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Evert Pot410 Gone (5.2.2019, 15:00 UTC)

410 Gone is a status code that can be used in cases where a resource is gone and never coming back. It’s a more specific version of 404 Not Found.

A good example for using 410 instead of 404 is when a resource was intentionally removed.

Using 410 can be helpful, because it signals to other people linking to you that the link is dead and should be removed. A 404 is the default for missing resources, and it can just mean that the owner of the site has moved the content and didn’t put the right redirects in place.

So to sum it up: 410 implies intent.

Example

HTTP/1.1 410 Gone
Content-Type: text/plain
Server: curveball/0.6.0

I deleted it and it's never coming back!

References

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Matthias NobackDDD Europe notes - Day 2 (1.2.2019, 11:50 UTC)

Cyrille Martraire: Domain modeling towards First Principles

This was a talk from the first day, but it required some more processing before writing about it. Cyrille is one of my favorite speakers. He's fast, funny and brings a lot of interesting topics to the table. So many that it's sometimes hard to keep following his train of thought, and writing down some notes at the same time.

A central concept from his talk was what he called the waterline between IT and the business. In a traditional scenario, developers get provided with "work" on a case-by-case basis. They don't learn about the general idea or plan, or even the vision, goal or need that's behind the "work item". They just have to "implement" it. It leads to badly designed code. But it also leads to the wrong solutions being delivered. If only developers could have talked with the people who actually have the problem for which they build the solution. Maybe there's another problem behind it, or maybe the business has provided the developer with a solution, instead of a problem. To higher the waterline means to get more involved with the customers and users, to understand their problems, and work together on a solution. Make sure you get involved.

When looking for the right solutions, investige the problems and use the following heuristic: "Consider the intensional alternative". Cyrille considers "intensional" a pedantic word and likes it. It's opposed to "extensional". Extensional corresponds to enumarating the results. Intensional means defining the predicate which will produce those results. Looking for intensional solutions means you'll end up with a better understanding of the problem. And also an automatable one.

While collecting these intensional aspects of existing business problems, as a developer you will be building a theory about that business. Cyrille warns against the illusion that a domain is simply a lot of information withs if-s on top. Business is messy, so we shoudn't be obsessed with rules. Some parts of a domain allow theorizing, some don't.

This nicely aligns with my own experience, trying to understand a business domain. Domain experts often aren't aware of the inconsistencies, or impossible rules they come up with. Once you bring in some logic, some rules seem reasonable but just aren't feasible. These may be areas where there's manual intervention in an otherwise automated system.

Another interesting concept Cyrille brought up was that of "skeuomorphism". He noticed that software solutions seem to continue building on technology from the past. Software systems often look like they're rebuilding a paper bureaucracy, but now it's digital. You can't really be "disruptive" if you don't think about radically different ways of solving some problem for the user. This was a bit of shock, because I realized that I often use "paper metaphors" to find out a possible solution for a design issue. Then again, maybe there's room for both - a paper metaphor as a design tool, yet a non-paper bureaucracy inspired software solution.

Maaret Pyhäjärvi: Breaking Illusions with Testing

Identifying herself as a "feedback fairy", Maaret talks about testing, in a very broad sense. It doesn't only cover automated testing, but also exploratory testing, and what you're doing with them. Tests don't break code, they break the illusions you have about it. The way Maaret explained testing, I immediately became scared of all the illusions I have about my code and that I should start breaking them.

I like how Maaret used the term "heuristics", like more DDD-ers do, to share with us how she and other testers do their work. It seems it's very common to share heuristics in the testing community. Very interesting! I don't think programmers share them as freely as they should.

Testing an application starts with realizing: you don't know much. So you have to create some sort of a map of what's there (functions, data, the platform, etc.). Start to discover, and never be bored. Always look for the interesting things, and "poke it until it pops".

In general, what you'll find is all kinds of illusions (they could be called "assumptions", I think). In testing an application ("it has high code coverage, so it's tested") but also in the general activity of developing software ("if we have this new feature, we'll earn more money").

Thinking in terms of illusions, I think most development teams are very good at them. We have all kinds of ideas about our code, our way of working, the application, our teammates, the company, etc. But they aren't really tested. It'll be smart to challenge them.

Also, looking at how others approach their problems is very useful. There will be a different perspective that you

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thePHP.ccBlast from the Past (1.2.2019, 07:00 UTC)
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Matthias NobackDDD Europe notes - Day 1 (31.1.2019, 19:00 UTC)

Eric Evans: Keynote ("Language in Context")

Starting out with the basics (words have meaning within a context; when we make the boundary of this context explicit we end up with a bounded context), Eric discussed two main topics: the Big Ball of Mud, and bounded contexts in the context (no pun intended) of microservices.

Legacy applications are always framed in a negative way, as if it's something to get away from. Personally, I've come to enjoy them a lot. However, there will always be the urge to work around legacy code. The Bubble Context (PDF) can be a great way of creating a new model that works well next to the already existing models. To keep a safe buffer between the new and the old model, you could build an Anti-Corruption Layer (ACL). A fun thing Eric mentioned is that the buffer works in two directions. The ACL also allows the old model to keep functioning without being disturbed by all the new things that are going on in the Bubble Context.

Given that a bounded context may or may not align with an actual subdomain, it may very well be that a legacy context is actually a Big Ball of Mud, with unified models, and simply just a lot of domain knowledge written between the many spaghetti lines that are in there. However, even though it is a mess, and it's getting harder to work with it every day, it may still be what you could call a "Mature Productive Context". The question is: is it still aligned with business views? If it is, we could improve at least maintainability and the cost of change by performing local refactorings. If it isn't, it'll be very hard to change anything. If the basic assumptions of the model change, rework will be very costly.

As a matter of fact, for a project I'm currently working on, we're looking into a module (or context), which requires some heavy refactoring, because it has become technically very hard to work with it. However, the business is still quite happy about it, and it's quite central to its processes.

An important Domain-Driven approach which can be used in the area of legacy code is where you analyze the different subdomains, and find out which ones are generic, and which ones are "core" to the business. As an example, in the aforementioned project there are actually two candidates for context-level improvements. One is related to Sales (which is the heart of this financial application), and one is related to Addressbook records (which is very much supportive to the Sales part). One could say it's even generic, in the sense that an off the shelf solution might be preferable. We wouldn't want to spend a lot of design or development effort there either.

Eric mentioned the term "Quaint Context" as a suitable name for a context that one would consider "legacy". It uses outdated technology probably, and has become hard to maintain. It won't be possible to make big changes there (as mentioned, because these basic assumptions can't easily be changed), so another good name could be "Patch-by-Patch Context".

With a microservice architecture, another option to deal with legacy contexts becomes what Eric calls the "Exposed Legacy Asset" (yet another nice term!). This will be a legacy application which starts to adapt to the microservices environment by producing messages that will be useful for actual microservices in that environment. For instance, database triggers could be used to produce events. The external events themselves don't have to be as low-level as the internal events that caused them.

Eric touches on several other interesting aspects of microservice architecture, but I wanted to briefly mention some other relevant ideas here. Eric looked back at 15 years of Domain-Driven Design and proposed that by now we maybe need a definition of DDD itself. He doesn't want DDD to be just a club, but asks for intellectual honesty. If you try to apply DDD and somehow it fails, you should share this story. If you're skeptical about some aspect of DDD, talk about it. I like how it boils down to focusing on the core domain, exploring models together, and speaking a ubiquitous language in an explicitly bounded context. Nice!

Rebecca Wirfs-Brock: Growing Your Design Heuristics Toolkit

This one was a workshop with limited access, so I was lucky I could attend it. Rebecca had spoken in a previous edition of the conference about heuristics, which triggered my interest in the idea. The workshop was about the process behind it. It had some interesting pointers, like a PDF about the concept and a book by Billy Vaughn Koen: Discussion of the Method. Definitely things to check ou

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Rob AllenUsing img2lambda to publish your Serverless PHP layer (31.1.2019, 11:02 UTC)

This interesting tweet by Clare Liguori came to my attention last week:

Img2lambda tweet2

This new img2lambda tool will take the layers of a Docker container and convert them to AWS layers for use in Lambda.

I poked around with Clare's example and updated my lambda-php project in order to understand how it works. I also rewrote my runtime's bootstrap to make it clearer.

The clever thing from my point of view is that you can build your PHP runtime layer locally using Docker and then publish the layers to AWS for use in your Lambda functions. This means you can now use the layer in different projects and have them all reference the same PHP runtime.

The magic of Docker

This is all done with the magic of Docker. Specifically, we create a Dockerfile that creates to containers:

  • A container to build the PHP binary
  • A container containing the layers that img2lambda will upload to AWS

Simplified, it looks like this:

# Build PHP in the Lambda container
FROM amazonlinux:2017.03.1.20170812 as builder

# PHP version of create
ARG ver="7.3.1"

RUN sed -i 's;^releasever.*;releasever=2017.03;;' /etc/yum.conf && \
    yum clean all && \
    yum install -y autoconf bison gcc gcc-c++ make libcurl-devel {etc}

RUN curl -sL https://github.com/php/php-src/archive/php-${ver}.tar.gz | tar -xvz && \
    cd php-src-php-${ver} && \
    ./buildconf --force && \
    ./configure --prefix=/opt/php/ --with-openssl --with-curl --{etc} && \
    make install && \
    /opt/php/bin/php -v

# copy php binary into /runtime/bin/php
RUN mkdir -p /runtime/bin && \
    cp /opt/php/bin/php /runtime/bin/php

# copy bootstrap files into /runtime
COPY src/* /runtime/


# Create runtime container for use with img2lambda
FROM lambci/lambda:provided as runtime

 COPY --from=builder /runtime /opt/

The first part download and compiles the PHP binary and puts it into /runtime/bin/php and also copies in the bootstrap files required to make the layer act as a Lambda runtime.

The second part simply copies all the files in /runtime in the first container into a new container. This new container containers a single layer which is our PHP runtime.

To build it we do:

$ docker build -t lambda-php-runtime .

The tag name can be anything.

Create the the layer in AWS

To create the AWS layer we use img2lambda:

$ img2lambda -i lambda-php-runtime:latest -r eu-west-2 -n lambda-php73

This tool will find the layer in the runtime container and upload it to eu-west2 and then store the identifier in output/layers.json which looks like this.

[
  "arn:aws:lambda:eu-west-2:66...06:layer:lambda-php73-sha256-e3c4...2e618b:1"
]

Using in Serverless Framework

You can take the ARN number and use it for your actions in serverless.yml like this:

functions:
  hello:
    handler: handler.hello
    layers:
      - "arn:aws:lambda:eu-west-2:66...06:layer:lambda-php73-sha256-e3c4...2e618b:1"

This is the way that we can re-use our PHP runtime in all our actions across multiple projects.

Serverless also allows you to import data from JSON files into your serverless.yml file, so you can also do:

functions:
  hello:
    handler: handler.hello    # {file name}.{function name}. In this case: hello() in handler.php
    layers:
      ${file(../php-runtime/output/layers.json)}

This has the advantage that when you re-build and upload PHP runtime layer, your project picks it up, which could also be convenient.

Testing locally

One of the benefits of building the runtime in Docker is that we can run it locally for testing our Lambda function. As our runtime container inherits from lambci/lambda:provided, we get an environment that looks very much like Lambda itself.

To test locally, we use another container and inherits from our runtime one and copies in the PHP files for our function. The Dockerfile looks something like this:

FROM lambda-php-runtime as function

COPY handler.php /var/task/src/handler.php

We create our cont

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