PHP

I read The Daily WTF every now and then and one story about bad logging code in PHP stood out to me. The post looked at some PHP code that was created to log a string to a file, but would have progressively slowed down the application every time a log was generated.

PHP is a great language as it allows you to put together code without easily shooting yourself in the foot. One downside of this ease of access is that it can allow beginners to put together code that works, but will ultimately cause problems in the long run. The PHP code given in the post is certainly an example of this.

I know that the goal of The Daily WTF isn't to fix problems found in code and is more of a satirical look at bad coding examples. I thought, however, that it would be good to look at the code and fix the issues it had.

If you've ever looked at the settings in a digital camera, or have experience with image processing programs like GIMP, then you may have seen a colour histogram. This is a simple graph that shows the amount of different shades of colour are present in the image.

They are created by looking at the number of colours in a given image and them mapping their red, green and blue values against a the frequency of their occurrence in the image.

Colour histograms are useful for looking at the overall colour distribution within an image and can also be used to simplify the colours of an image by restricting how much of a certain colour is allowed based on its frequency.

I was writing unit tests for a API mapping function recently and came across this interesting issue. The code I was writing tests for was in a legacy codebase that I was making changes to, and it made sense to have some unit tests in there before I started work to ensure everything worked before and after.

The mapping function in question would take a value as input and return another value as the output. The code seemed like it should work, but then applying certain values to the mapping function it would produce an incorrect result.

The PHP Standards Recommendations (called PSR) are a set of standards that aim to make certain aspects of working with PHP easier. They include things like coding standards (PSR-1), sending HTTP requests (PSR-7), and the autoloading standard PSR-4.

PSR-4 describes the ability to include PHP classes based on their file paths. This means that instead of manually including every class file you need, you can write an autoloader that will do this for you.

The key bits of information are the namespace and the name of the class. Using this information you can then look up and include the class you need as the code is running.

Generating a PDF document from a web page through PHP can be problematic. It's often something that seems quite simple, but actually generating the document can be difficult and time consuming.

There are a number of libraries available that allow you to generate PDF documents, but in reality they solve one problem and introduce several more. Packages exist as either HTML to PDF converters or allow you to generate a PDF by placing elements into the document.

Generating a PDF manually is not normally a good way to go just due to it being a very time consuming process and is difficult to test. You will probably have to spend time creating a rendering engine just for this purpose, and that will take time to create and maintain.

Working with logic surrounding dates can sometimes be difficult and it's fairly common to come across really subtle date and time based bugs.

I was recently shown a bug in a PHP application that looks like it should be working at face value, but doesn't actually produce the correct result.

The issue in question was surrounding a date comparison. A collection of objects containing dates were compared in order to find those dates that were less than a month old. This worked fine in testing since all testing dates were less than a month old. After the system was in use for a number of months it became clear that the check wasn't working so further investigation was needed.

Reflection is used to gather more information about code during the runtime of the program. This allows code to inspect itself and to make small modifications, which is useful in a variety of situations.

This is possible in PHP thanks to the reflection classes, which are built into core. PHP is capable of using reflection to inspect all types of classes, object, functions, variables and even the recent addition of Fibers. Using the reflection classes we can find out the internal structure of a class that an object is part of, including properties, methods constants as well as what sort of class we are dealing with. Reflection works even if the property of method is private or protected.

This post will concentrate on objects (and their associated classes) as the code used to inspect objects can generally be applied to other forms in PHP.

I use sites like CodePen and JSFiddle all the time to write JavaScript and CSS, but I've not seen a similar site for writing PHP applications. I have used 3v4l.org to test small scripts using different versions of PHP, but it doesn't allow dependencies to be added and doesn't have a nice editing interface.

Recently, I found a site called PHPSandbox that allows users to create PHP applications that can be run in the same way as applications on CodePen. This includes using composer to inject dependencies into the application and a nice little editor interface to see the output and logs from the application.

PHP 8.1 comes with a few new additions to the language, and one that I have seen get the most attention is fibers. This is a feature that allows PHP code to be executed in a concurrent thread, with the ability to pause and resume that code at will.

Using fibers doesn't mean that the code runs in parallel, rather that the code is executed away from the main thread in a virtual or green thread. These are threads create by and executed by the PHP VM, rather than being executed by the CPU and managed by the underlying OS. This lightweight thread of execution is also called a coroutine and are executed in sequence, rather than being parallel.

Fibers are intended to eliminate the distinction between synchronous and asynchronous functions in PHP and provide a petter mechanism to manage blocking code.

PHP has a built in debugging and testing tool called assertions, which is essentially the assert() function and a few configuration options.

With this feature you can add additional checks to your application whilst you are developing it so that when you deploy to production you can be sure that things will run correctly. It is simple to run and allows you to embed testing code within your production code without having an adverse effect on performance.

I've seen the use of assert() in a couple of open source PHP projects, but had not really dug into how it works or what it does. As it turns out, assert() is actually very useful and can also be found in other languages like C/C++, Python and JavaScript.