What should I do if php does not support multi-threading?

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 The parameter specifies the thread-safe method to use when compiling PHP.

Recommended: php server

Thread safety

Multi-threading is a factor that makes the program restless. Before using multi-threading, first Thread safety issues should be considered:

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.

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

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

2. A thread obtains an array with a length of 1;

3. B thread obtains an array with a length of 1;

4. A thread pops out array elements $a = array_pop($arr); $a = 'a';;

5. B thread also pops out array elements $b = array_pop($arr); $a = null;;

6. At this time, a supernatural event occurred in the B thread. The array length was obviously greater than 0, or nothing was popped;

PHP implementation

The thread safety implemented by PHP mainly uses the TSRM mechanism to isolate global variables and static variables, and copies global variables and static variables to each thread. One copy, each thread uses a backup of the main thread, thus avoiding variable conflicts and 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.

Classes and methods

PHP encapsulates threads into the Thread class. Thread creation is achieved by instantiating a thread object. Due to the encapsulation of the class, variables can only be used through the constructor. Pass in, and the thread operation results also need to be passed out through class variables.

The following introduces several commonly used Thread class methods:

• run(): This method is an abstract method. Each thread must implement this method. The thread starts After running, the code in this method will be executed automatically;

• start(): Call this method within the main thread to start running a thread;

• join(): Each thread is executed asynchronously relative to the main thread. Calling this method will wait for the thread execution to end;

• kill(): Force the thread to end;

• isRunning(): Returns the running status of the thread. It will return true when the thread is executing the code of the run() method;

Because of the implementation of thread safety , after PHP's multi-threads start running, they can no longer communicate through the shared memory space, and threads cannot be reused through inter-thread communication, so I think PHP's "thread pool" is meaningless. The Pool class that comes with the extension is a class that manages multi-thread allocation and will not be introduced here.

The above is the detailed content of What should I do if php does not support multi-threading?. For more information, please follow other related articles on the PHP Chinese website!