Getting Started with PHP: Coroutines

With the continuous development of the Internet and the increase of high-concurrency scenarios, PHP, as a high-performance, easy-to-learn and use language, has received more and more attention and application. PHP's coroutine technology is one of its important tools for high concurrency processing. This article will introduce you to the basic concepts, implementation principles and application scenarios of PHP coroutines.

1. What is coroutine technology?

Coroutine technology is simply the abbreviation of "coroutine". It is a lightweight thread that can switch execution between multiple coroutines in the process instead of preemptively interrupting execution. and switch context. Compared with threads, the creation and destruction of coroutines has less overhead and does not require operating system scheduling. It can achieve efficient collaborative concurrency in synchronous IO and asynchronous IO.

The implementation principle of coroutine technology is to use the generator function (Generator) and the yield keyword. When the yield statement is executed, the current running state is saved, switched to other coroutines for execution, and then restored. In the saved state, continue executing the code after yield. Therefore, coroutine technology is essentially a user-mode thread that can control the execution flow of the program more flexibly.

2. Basic use of PHP coroutines

Starting from PHP5.5, native support for coroutines has been introduced. By using the yield keyword and generator function, it can be implemented simply and intuitively. Basic functions of coroutines. For example, the following example implements a simple coroutine switching and prints the number sequence from 1 to 10:

function numbers() {
    for ($i = 1; $i <= 10; $i++) {
        yield $i;
    }
}

$gen = numbers();
foreach ($gen as $num) {
    echo $num . PHP_EOL;
}

In this example, we define a generator function numbers() to implement the number sequence from 1 to 10 sequence of numbers, and then creates a generator object $gen, which is traversed through the foreach loop. Each time the yield statement is executed, the current running status is paused and saved, and then switched to the next coroutine to continue execution.

3. Advanced usage of PHP coroutines

In addition to basic coroutine switching, PHP coroutines also support many advanced usages, such as coroutine sharing, coroutine pool, and coroutine scheduler wait. These functions can help us more flexibly implement the processing of various high-concurrency scenarios and improve the overall performance and efficiency of the system.

1. Coroutine sharing

Coroutine sharing refers to sharing certain data or resources between multiple coroutines, such as shared database connections, shared memory data, etc. This function can be implemented through the coroutine context (Context). The context saves the execution status and related data of the coroutine and can be transferred and shared between different coroutines.

2. Coroutine Pool

The coroutine pool refers to a set of reusable coroutines that can be reused during the life cycle of the coroutine, avoiding the need for coroutines Frequent creation and destruction overhead. The coroutine pool can be implemented through polling or Event Loop. Each time an idle coroutine is taken out of the coroutine pool to perform a task, it is returned to the coroutine pool after the task is completed.

3. Coroutine scheduler

The coroutine scheduler refers to a component responsible for coroutine switching and scheduling. It can implement coroutines according to different scheduling algorithms. Priority, concurrency, error handling, etc. Commonly used coroutine scheduling algorithms include: preemptive scheduling, collaborative scheduling, time slice rotation scheduling, etc.

4. Application scenarios of PHP coroutines

PHP coroutine technology has extensive and important applications in high-concurrency scenarios, such as: high-traffic Web applications, asynchronous IO processing, high concurrency Database operations, message queue services, etc. These application scenarios all require the use of coroutine technology to improve the performance, concurrency and scalability of the program and effectively cope with business growth and changes.

In short, PHP coroutine technology, as a lightweight and efficient concurrent programming model, is being widely used and applied by more and more developers and enterprises. In the future Internet era, PHP coroutine technology will gradually develop and expand, bringing more opportunities and challenges to system performance optimization and efficiency improvement.

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