Why You Should Use Asynchronous PHP
The Difference Between Synchronous vs. Asynchronous Programming
Before we discuss the merits of asynchronous PHP, let’s quickly review the differences between the synchronous and asynchronous programming models. Synchronous code is sequential. Individual tasks must be completed before you can start another one. In asynchronous code, multiple tasks can be completed simultaneously, which can dramatically boost application performance and user experience.
What Is Synchronous PHP?
Synchronous PHP refers to PHP code that is written using the synchronous model. PHP was originally created to support synchronous development, so most PHP developers are used to writing only synchronous code with the language. Prefork with either mod_php with Apache or php-fpm with either Apache or Nginx.
Looking for the basics of PHP? Check out this blog, PHP Development Basics: What Is PHP, Why Is It So Popular, and What Are the Advantages of PHP?.
What Is Asynchronous PHP?
Asynchronous PHP refers to PHP code that is written using the asynchronous model. By using extensions such as Swoole, or a PHP framework such as ReactPHP, you can make PHP accept requests and responses asynchronously, using event loops.
What Is the Main Difference?
In many applications, there’s a lot of time when a CPU sits idle during I/O tasks. The idea behind aynchronous PHP is to take full advantage of all available CPU cycles by keeping non-blocking I/O tasks running in the background, and letting the CPU process other tasks as it’s waiting for data and instructions needed to complete the I/O tasks. With synchronous PHP, the CPU would process only the I/O task. And when it was done, it would process the next task in its queue.
Using asynchronous PHP results in lightning-fast performance compared with applications written using synchronous PHP. In some benchmarks, you can increase throughput by 100 times, by enabling asynchronous PHP using Swoole, than using a process accelerator such as php-fpm in synchronous code. That’s because php-fpm does not support asynchronous, real-time communications using protocols such as Websockets.
Which PHP Should You Use?
As with most questions around runtime, web servers, and programming in general, the decision to use synchronous or asynchronous PHP will vary between use cases. To use asynchrounous PHP, your code needs to support it. Most of the extensions that PHP developers are accustomed to using make calls that block the process—also known as blocking I/O--which make the asynchronous model impossible.
For example, to leverage Swoole, when a call that requires I/O is encountered, it needs to send that call to the background and continue onto the next instructions. When the data comes back from the I/O call, Swoole needs to return control to the I/O call that had been sent to the background, so it can hand the requested data to the process. Rewriting your code to support asynchronous processes may require some refactoring to work. However, the time savings you gain in the future may be worth it.
Projects to Get Started with Asynchronous PHP
Since your code has to be written in a way to support asynchronous processes, you’ll need to utilize a project that can do that. Here are our top-three recommendations:
- Swoole – Coroutine PHP ansychronous programming framework.
- Reactphp – Event-driven, non-blocking I/O with PHP.
- Amphp – Non-blocking concurrency framework for PHP.
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