Getting Started with PHP: Multi-Process Communication

As a server-side language, PHP often needs to handle a large number of concurrent requests. In order to better cope with high concurrency scenarios, PHP supports multi-process and multi-thread programming. This article will introduce the basic concepts, common methods and implementation techniques of PHP multi-process communication, and help PHP beginners quickly master multi-process programming skills.

1. Basic concepts of multi-process communication

1. Process
   Process (process) is a basic concept in the operating system and refers to a running program instance. Each process has its own independent memory space, running status and resource usage, without interfering with each other. In PHP, each PHP script can be regarded as a process.
2. Inter-Process Communication
   Inter-Process Communication (IPC, Inter-Process Communication) refers to the way of data exchange and coordination between different processes. In multi-process programming, inter-process communication is the key to achieving process synchronization and data sharing.
3. Process Synchronization
   Process synchronization (process synchronization) refers to the process of coordination and synchronization between multiple processes to complete a certain task. In multi-process programming, process synchronization is an important means to ensure the sequential execution of processes, avoid resource competition, and avoid deadlocks.
4. Data sharing
   Data sharing (data sharing) refers to the way in which multiple processes share the same data. In multi-process programming, data sharing is the core goal to achieve inter-process communication and collaborative task completion.

2. Common methods for PHP to implement multi-process communication

1. Named pipe
   Named pipe (named pipe) is a special file type used on the same computer Communication between different processes on the machine. Named pipes can safely pass one or more structured sets of data. In PHP, named pipes can be created using the posix_mkfifo() function.
2. Shared memory
   Shared memory (shared memory) refers to the same memory area that multiple processes can read and write together. In PHP, you can use the shmop_* series of functions to achieve operations such as creating, reading, writing, and deleting shared memory.
3. Semaphore
   Semaphore (semaphore) is a mechanism in the operating system for process synchronization and mutual exclusion. In PHP, you can use the sem_* series of functions to implement resource allocation, access, and release operations between processes.
4. Message queue
   Message queue (message queue) is a way of communication between processes, which can asynchronously transmit structured messages between multiple processes. In PHP, you can use the msg_* series of functions to implement operations such as creating, reading, writing, and deleting message queues.
5. Socket Socket
   Socket (socket) is a method of inter-process communication that can communicate between different machines. In PHP, you can use the socket_* series of functions to implement Socket programming and complete TCP/IP network communication and data transmission.

3. PHP multi-process programming implementation skills

1. Use the pcntl_fork() function to create a child process
In PHP, you can use the pcntl_fork() function to create a child process. The parent process will copy its own memory space to the child process, but the memory of the child process is independent of the parent process. You can use the pcntl_wait() function to wait for the child process to complete the task to ensure that the result returned is correct.

2. Use signal processing functions to handle process exceptions
In PHP multi-process programming, child processes may exit abnormally for various reasons. In order to catch these exceptions and handle them in time, you can register a signal handling function. When the child process receives a signal, it will automatically call the corresponding signal processing function for exception handling.

3. Reasonable use of mutex locks
In multi-process programming, in order to avoid resource competition and data inconsistency, mutex locks (mutex) need to be used to achieve synchronous access between processes. When using mutex locks, avoid deadlocks and resource leaks.

4. Avoid a large number of IO operations
In multi-process programming, if a large number of IO operations are processed, it is easy to cause system crashes and performance degradation. Therefore, when writing PHP multi-process programs, you should try to avoid frequent IO operations, such as network communication and disk reading and writing.

4. Summary

This article introduces the basic concepts, common methods and implementation techniques of PHP multi-process communication. When implementing multi-process programming, you need to pay attention to important aspects such as communication methods between processes, process synchronization and data sharing issues, signal processing, and mutex locks. Only by flexibly mastering various communication methods and techniques can we write high-quality, high-performance PHP multi-process programs.

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