Statamic Throughout this article we will be creating a Statamic modifier that Using Modifiers in Antlers Dynamic Bindings Statamic Throughout this article we will be taking a closer look at passing Home Articles Meerkat Contact. Open menu. Introduction PHP is a popular server-side language that is fantastic for web applications.
The Language PHP is an interpreted language. Step 3 The web server gets the request and analyzes the request information. Step 7 Apache receives the output from PHP and sends it back over the Internet to a user's web browser.
Step 8 The user's web browser receives the response from the server, and renders the web page on a computer or device. Conclusion This concludes this first article in a little series about the basics of programming with PHP. Name optional. Submit Comment. There are no comments. Be the first to comment! Read full article.
March 27, Laravel: Calling Artisan Commands From Your Application This little tip will show you how to run Artisan commands from within your applications code, if you need to. John Koster. This is why you should keep concurrency in mind when working with a PHP application. And concurrency like memory management has more than one implication with PHP.
Multitasking is the idea that you can perform a set of computer tasks faster if you do them at the same time. PHP applications rely on this concept a lot to do computing intensive tasks. So multitasking comes down to creating requests for these extra tasks that we need to do. How does this work? Well, as you can see in the above diagram, you have an initial request to your PHP application. This initial request will cause the PHP application to generate other subrequests to itself.
These other subrequests are our new application tasks. They run at the same time as our initial request. In a CMS, a cron job is a task that you scheduled like publishing a future post in the future that you need your CMS to handle. The most common one is resource starvation which means exactly what the name suggests. It refers to your concurrent PHP processes not having the resources they need to run well or at all. And your PHP application takes on average 50megs of memory during its execution.
This means that, in theory, your server can only handle six concurrent executions. So what happens if your server needs to process more than six scripts at a time? Well, at this point, it depends on how your host configured your server. It could just slow down or it could outright die. Yes, you could its reduce memory usage. Resource starvation is more of a server configuration issue than an application issue.
Another issue to be aware of with concurrency is race conditions. A common example of a race condition is tracking page views. That said, most types of tracking are susceptible to race conditions. The page view tracking code is in pink. In it, we fetch the current number of page views, increment the number by one and then save the value again. This is all pretty straightforward so far. What happens if there are multiple executions of our page view tracking PHP code at the same time?
Everything looks ok in this timeline. We have multiple executions of our PHP code, but none of the pink bars overlap. Each execution is able to fetch the current number of page views, increment it by one and then save it again. But what happens if multiple executions of our PHP code overlap? Well, this is where things start to break down.
As you can see, the execution of our page view tracking PHP code overlaps now. This code overlap is our race condition. Because of it, the page view increment from the second process is incorrect. So it counts the same number of page views as the first process. Because of the race condition, the third process also overwrites the number of page views recorded by the second process. If we had more concurrent processes, this would compound the problems caused by the race condition.
The result is an inaccurate tracking of the number of page views. So how do we fix the race condition in our page view tracking PHP code? The obvious solution is to not do it and use an external service like Google Analytics.
Well, the problem with race conditions is that there are countless ways to fix them. The key to fixing a race condition is the concept of mutual exclusion. Mutual exclusion is itself a property of larger topic called concurrency control. And the point of concurrency control is to ensure that concurrent operations like our tracking of page views generate the correct results. Mutual exclusion is the idea that only one execution can enter a critical piece of code at a time.
And how can we implement mutual exclusion with PHP? One of the common ways to implement it is with a lock. You use a lock to limit the access to a resource. In this scenario, this would be the number of page views that we only want one process to access at a time. This timeline shows what happens to our page view tracking code when we use a lock.
The yellow bar in our timeline represents the time spent waiting for the other execution to release the lock. Our page view tracking code can only begin when that happens. We will be referring to the PHP lines of code as statements.
PHP statements end with a semi colon ;. If you only have one statement, you can omit the semi colon. If you have more than one statement, then you must end each line with a semi colon. For the sake of consistency, it is recommended that you always end your statement s with a semi colon. PHP scripts are executed on the server. The output is returned in form of HTML. Skip to content. Report a Bug.
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