PHP

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.

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.

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.

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.

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.

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.

I was looking for a function that searched an array for another array, and after not finding one I decided to write it. What I was looking for was a function that took a smaller array and searched for that exact sequence of items in a larger array. As it happens, PHP does have a number of array search functions, but they didn't produce the correct result.

The array_search() function does accept an array as the needle to be searched for, but this does a multi-dimensional search instead. I also saw some techniques using array_intersect() or array_diff(), and although these functions were able to find one array inside another I was interested in the sequence.