Posts about the server side scripting language PHP
From the drawers of "I didn't realise how complicated that was" I was wondering the other day how to draw a line using just pixels. This turned out to be more complicated than I thought.
Normally in PHP you would use the imageline() function to draw a line between two points. The following block of code creates and image and draws a white line from the coordinates 50x,50y to 200x,150y.
Following on from by previous post about sorting colors I decided to take another step towards sorting colors by segmenting the data to create a further dimension to the multi-dimensional array.
The array is already split into segments based on the hue of the color, but we can further split this by separating out saturation and value into separate arrays within hue. To do this we set the saturation or value to be a constant and push them into separate arrays.
The new code looks like this. Please excuse the duplication of code here. This is just a simple example to show how the array is put together.
The last time I looked at sorting colors I had produced a nice band or sorted colors, but to do so I had essentially removed a third of the data from the color information. This meant that there was no white or black colors in the band of sorted colors.
After a bit of thinking on how to solve this I hit upon a way of using a two dimensional array of colors to filter the colors into blocks. This would allow the missing color information to be rendered correctly, and would only mean a small amount of work to allow it to work with the rendering function used in the previous examples.
I could easily just generate every color available and use that as the data. What I wanted to generate was a random assortment of colors that would represent the sort of data being produced by a system or other input.
I've been using PHP for a number of years and have seen the same things being done with return values from functions over and over again. I have always thought of this as pretty standard, but the more I think about it the less it makes sense. Looking back over my career I am quite sure that a few serious bugs could have been avoided if I had not mixed return types.
As PHP is a loosely typed language this gives the developers the ability to change the type of value that is returned from a function. This happens quite often within the PHP codebase itself as many built in functions will return false if an error happened.
A common practice in userland code is to return false from a function if something went wrong. This might be because it is encouraged in PHP itself.
I wanted to impart a piece of advice to do with validation and formatting of user input, although I've never seen anyone suggest it. I guess it would come under the single responsibility principle so it might seem obvious to some people. There can be reasons why this might at least seem like a good idea at the time.
Essentially, if you want to validate that something is correct, don't format it at the same time. These two actions should be done in separate functions or even classes. I hope to demonstrate that using a single function validate and format anything is a bad idea. I'll mainly be using PHP to demonstrate this, but the principle should be pretty much the same in any language.
Take the following function called isValid(). This is an arbitrary and simple example but shows validation and formatting in use in a single function.
Following on from my last post about sorting colors I have been thinking about different ways of sorting colors. I have been looking at interfaces that allow people to select colors and they will quite normally have a band of colors that does look nicely sorted. As it turns out this is perfectly possible to do if the colors are normalised to remove light and dark variations of different colors.
The easiest way to remove different amounts of lightness and darkness from a color is to convert it to the HSV color space. This way we can just set the value (brightness) and saturation (amount of grey) to be 1. This will change the color by simply removing any information that does not pertain to the actual color. For example, a color that is a very light shade of blue will be changed to be simply blue.
Sorting colors is the sort of thing that you never really think about until you need to do it. Sorting a bunch of items by their color is useful in a number of applications, but the simplest is just to display items to the user in a more controlled manner. As it happens sorting with colors is a much more complex topic than I originally thought and required digging into quite a bit more maths than I expected.
Incidentally, there is a whole world of color maths that I didn't know existed until I started looking into this. It was worth learning about though.
To start with, I created a little Color class so that I could have a standard way of storing a color. This just takes the red, green and blue values for a color and allows a simple way of accessing those values.
Deployer is an amazing tool that is used to deploy websites (hence the name). I have looked at other tools, but because Deployer is built and run using PHP, using it to deploy PHP sites makes sense. It also means that I don't have to figure out complex XML documents or learn Ruby just to understand what the deployment is doing.
I have been using Deployer for a little while now to deploy my own site but I have been using the root user to accoumplish the deployments to get around any permissions issues. When I sat down with the developers at work we looked into how to setup the server so that deployments could be run without giving the tool unfettered access to the server. To this end we set out a plan to create a 'deployer' user on our servers that would be the user Deployer uses to deploy sites.
Collecting Information
The PHPNW 2017 Conference was run over the weekend of the 30th September to 1st October at the Manchester Conference Centre and I went along to participate. PHPNW has now been going for 10 years and it looks like this will be the last (more on that later) but this year was just as good as ever.