PHP

Let's say you had a class that you wanted to use, but there was some sort of error in creating the object. This might be that the wrong parameters were passed, or the third party service (eg. a database) wasn't available at the time of creation.

If this happens you'll obviously want to handle the error correctly, but the question is would you throw an exception in the constructor or handle the error condition elsewhere?

Note that this article will talk about PHP, but the same discussion applies to other languages that implement OOP principles.

 Question

What does the following code print out?

function arrayPrint($array)
{
   echo implode(' ', $array);
}

$arrayA = [1, 2, 3];
$arrayB = $arrayA;
$arrayB[1] = 0;
arrayPrint($arrayA);

Using frameworks to handle the authentication of your PHP application is perfectly fine to do, and normally encouraged. They abstract away all of the complexity of managing users and sessions that need to work in order to allow your application to function.

That said, it is important to take a step back and understand how authentication works in PHP. This allows you to more accurately debug problems with framework authentication systems that you make common use of.

Creating an authentication system using PHP is pretty simple since PHP has many of the features and functions built in. In fact, frameworks will simply wrap this feature set into a coherent authentication model that can be expanded to introduce new features.

In this article I will go through the steps required to create an authentication system using PHP and MariaDB. I will assume you have some knowledge of PHP, but that you want to know more about how to authenticate users.

A sparkline is a very small line graph that is intended to convey some simple information, usually in terms of a numeric value over time. They tend to lack axes or other labels and are added to information readouts in order to expand on numbers in order to give them more context.

Sparklines tend to be around 20-30 pixels height and up to 150-200 pixels wide. The are generally best when you want to show between 5 and 15 items as adding more items to such a small graph can make things a little messy.

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.