Will PHP support multi-threading in the future?

Multi-threading in PHP

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

Thread safety (Recommended learning: PHP programming from entry to proficiency)

Multiple threads are 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 refers to the ability of a function or function library to handle correctly when called in a multi-threaded environment. Shared variables between multiple threads enable program functionality to be completed correctly.

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 the array elements $a = array_pop($arr); $a = 'a';;

B thread also pops array elements$b = array_pop($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

The thread safety implemented by PHP is 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 eliminating Thread safety issues may arise.

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.

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