How to multi-thread in php

PHP does not support multi-threading by default. To use multi-threading, you need to install the pthread extension. To install the pthread extension, you must use the --enable-maintainer-zts parameter to recompile PHP. This parameter is specified when compiling PHP. Use thread safety.

Multi-threading is a factor that makes the program restless. Before using multi-threading, you must first consider thread safety issues:

Thread safety: Thread safety is a term in programming, which means that when a function or function library is called in a multi-threaded environment, it can correctly handle sharing between multiple threads. variables so that program functions can be completed correctly. (Recommended learning: PHP video tutorial)

In traditional multi-threading, since multiple threads share variables, the following problems may occur:

There is a global Array $arr = array('a');;

A thread gets the array length to be 1;

B thread gets the array length to be 1;

A thread pops out Array element $a = array_pop($arr); $a = 'a';;

B thread also pops array element $b = array_pop($arr); $a = null;;

At this time, a supernatural event occurred in the B thread. The array length was obviously greater than 0, or something was not popped;

PHP implementation

PHP implementation of thread safety Mainly, the TSRM mechanism is used to isolate global variables and static variables. Global variables and static variables are copied to each thread. Each thread uses a backup of the main thread, thereby avoiding variable conflicts and also There will be no thread safety issues.

PHP's multi-thread encapsulation ensures thread safety. Programmers no longer need to consider adding various locks to global variables to avoid read and write conflicts. It also reduces the chance of errors and makes the code written more secure.

But the result is that once the sub-thread starts running, the main thread can no longer adjust the running details of the sub-thread, and the thread loses the ability to transmit messages between threads through global variables to a certain extent. .

At the same time, after PHP turns on the thread safety option, there will be additional losses when using the TSRM mechanism to allocate and use variables. Therefore, in a PHP environment that does not require multi-threading, use the ZTS (non-thread safety) version of PHP. Just fine.

The above is the detailed content of How to multi-thread in php. For more information, please follow other related articles on the PHP Chinese website!