PHP

Posts about the server side scripting language PHP

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Installing SimpleSAMLphp Using Composer

11th July 2021 - 8 minutes read time

Security Assertion Markup Language (SAML) is a standard that passes authentication credentials between hosts and essentially allows for a single sign on solution to be created. The standard uses XML files that get passed between the authentication system (known as the identity provider or IdP) and the service users want to sign into (known as the service provider or SP). 

SimpleSAMLphp is an open source application that implements SAML mechanisms and allows for the authentication system to be created as well as some administration tasks to be performed. The system is robust and battle tested, having been integral to the open source authentication systems for a number of years.

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Create Checksums Using The Luhn Algorithm In PHP

16th May 2021 - 14 minutes read time

The Luhn algorithm was created by Hans Peter Luhn and is a way of creating a simple checksum for a number. This algorithm, also known as the mod 10 algorithm, is used in a wide variety of applications but is commonly associated with credit card numbers.

If you look at the numbers on the front of your credit card the last digit on the right is the checksum. An algorithm is done on the other numbers and if the checksum is the same then the number is considered valid.

Outside of credit card numbers, the Luhn algorithm can be used to create a checksum on any number that you want to store. It is especially handy when you want to give users a number that they will be hand typing into a computer. The checksum helps spot any errors in typing in the number before that number is processed. The good thing about the Luhn algorithm is that it doesn't matter how long the number is so it will work with any kind of digit sequence.

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Swapping Between Different Composer Versions

10th May 2021 - 2 minutes read time
I had an issue I was trying to debug today and needed a way to swap between different versions of composer. Composer is one of the few things that I install globally so it was locked at a particular version on the machine I was using. There has been some significant changes between version 1 and version 2 and it isn't quite safe to use a composer 2 package on a platform that has composer 1 installed.  As some projects I'm working on haven't been upgraded yet I needed a way to swap between versions whilst this work was being done.
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Creating A Game With PHP Part 4: Side Scrolling Shooter

10th March 2021 - 12 minutes read time

As another step up from the game of snake I created in my last post I decided to try my hand at creating a side scrolling shooter. Just like my other posts, this is an ASCII based game played on the command line.

A side scrolling shooter, if you didn't already know, moves a scene from right to left across the screen with enemies moving with the scene towards the player's ship, which is on the left hand side of the scene. The player can fire bullets towards the enemies so remove them from the scene.

In order to create a side scrolling shooter we need to define a few elements.

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Seeding Random Numbers in PHP

9th March 2021 - 7 minutes read time

Computers are not that great at creating random numbers as the methods they use are deterministic. That is, they start from a number (called a seed) and apply maths to that number to generate pseudorandom numbers. Most random numbers generated by computers programs use a seed provided by the system, which is generally the current time. If you can guess the initial value then you can start to work out what the random sequence of numbers generated is. Most random numbers, are therefore not suitable for encryption.

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PHP Strict Types

28th February 2021 - 6 minutes read time

In December 2015, PHP 7 introduced scalar type declarations and with it the strict_types flag. This flag can be used to enforce the type of value passed to functions. Although I have seen it in action in the past, I have never actually used it before so I decided to look into it a little to see what it was about.

For some background, types are not strictly enforced in PHP. This means that it is not only possible to swap the type of a variable from one type to another, but it is also possible to swap a variable of one type to another depending on the context being used. Programmers getting started in PHP will spot this when attempting to print out a boolean value as this will be cast to an integer before being printed out. This means that when attempting to print 'true' PHP will instead print out '1'. PHP will automatically coerces values to be one type to another when passing values to functions.

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PHP instanceof Operator Tips

26th January 2021 - 8 minutes read time

The instanceof operator in PHP is great at making sure you are looking at a type of object before acting on it. Whilst it's straightforward to use on its own, using it can lead to some undesirable side effects.

As a basic example, let's create a couple of interfaces and classes to show the instanceof operator in action. Rather than just have some test names I am using object names that you might find in a system. This consists of User and Order that might form part of a commerce system.

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Steganography With Images In PHP

15th January 2021 - 18 minutes read time

Steganography is the practice of placing a secret message inside another message and only by looking at the original message in a different way can the hidden message be seen. This might be as mundane as writing a page of text and hiding a message in the text using the first letter of every sentence. Only by collecting the first letter of each sentence together can the hidden message be seen and read.

Modern steganography is defined as hiding a message (or file) inside a file. For example, you might look at an image and see an image, but if a message has been hidden you would also be able to extract it if you know where to look.

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Color Sorting In PHP: Part 6

2nd January 2021 - 17 minutes read time

I finished my last post on sorting colors using PHP looking at incorporating all three dimensions into the display of the colors. This lead to some interesting displays of colors in discs using different shapes or lengths as an indication of the color in question. It was still lacking actually rendering out the third dimension in any meaingful way though.

As I am essentially looking at three dimensional data I thought about displaying the data as a cube in a 3D engine. I could then map the three dimensions of colors (red, green, blue) into the three dimensions of the 3D engine (x, y, z). This means creating a 3D scene with random color data and rendering that scene out. Funnily enough, there aren't a lot of people writing 3D rendering engines in PHP so I looked into writing a very basic version that would just show point data.

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Extracting Data From An MP3 With PHP

28th December 2020 - 27 minutes read time

I was looking at a media player on my phone the other day and was watching the waveform of the music shown on screen. This was a simple indication of the progress through the track and appeared to show quiet and loud sections of the track I was listening to. This got me thinking about how to extract this information as the media player I was watching must do this in real time in order to actually play the data, not just render this representation of the music.

After a bit of research into the MP3 file format I found that the file format is complex, but straight forward enough to process, so I decided to try and extract the data using PHP. I have seen a few techniques to extract the data from MP3 using PHP, but these largely involve applications like ffmpeg to convert the audio format into something like a WAV file, which is then processed.