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Multithreading is a form of program execution in which a single process creates multiple threads and they execute simultaneously. This tutorial will discuss multithreading in PHP and show you how to implement it.

ParallelImplementing multithreading in PHP using the Parallel Concurrency Extension

Using Parallelthe Parallel Concurrency Extension, we can implement multithreading in PHP.

This extension provides an interpreter thread parallel\Runtime. We can parallel\Runtime()create an object from the class, thereby creating a thread.

This class provides a method run(), which schedules tasks to run in parallel. We can pass Closureas a parameter to runthe method.

This parameter is generally called task, and we can also specify an array as the second parameter of the method. The contents of the array are passed to the task.

There are some requirements before downloading Parallelthe Parallel Concurrency Extension. The PHP version should be 8.0 and Zend Thread Safe (ZTS) should be enabled.

<pthread.h>The header is another requirement. We can pecldownload the extension from as shown below.

pecl install parallel

We can use forloops to test parallel execution of a program.

For example, we can run()run a loop inside a method and another loop outside that method. In this case, the code execution will be parallel.

For example, create parallel\Runtimean object of the class $rtand then use the object to call run()the method. In run()the method, write an anonymous function.

First, write a forloop to print the symbol 50 times inside the function +. Next, run()outside the method, write another forloop to print -the symbol 50 times.

Since run()the loop inside the method runs in a separate thread, run()the loop outside the method will be executed simultaneously. As a result, -the and +symbols are printed simultaneously, as shown in the output section below.

Therefore, we can use the Parallel Concurrency Extension to implement multithreading in PHP.

Sample code:

$rt = new \parallel\Runtime();

$rt->run(function(){
 for ($i = 0; $i < 50; $i++)
 echo "+";
});

for ($i = 0; $i < 50; $i++) {
 echo "-";
}

Output:

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

popen()Using functions to implement multithreading in PHP

We can popen()open parallel processes in PHP using the function.

This function forks the process to achieve parallel processing. The processes do not share resources.

In this way, we can implement multithreading in PHP. popen()The function creates a pipe to the forked process.

We can iterate over popen()the function and create multiple processes to implement multithreading. popen()The function takes commandas the first parameter and modeas the second parameter.

Mode can be either ror w.

For example, create a loop that forloops five times. Inside the loop, create another loop that loops five times for.

Inside the sub-loop, create an array $processto store popen()the functions. Set the PHP file message.phpand rmode as the first and second parameters.

Next, create another sub-loop and pclose()close it using the function $process.

Here, five processes are executed in parallel in the first sub-loop. The processes pclose()are terminated in the second sub-loop using the function.

This is how we use the function in PHP popen()to achieve multithreading.

Sample code:

for ($i=0; $i<5; $i++) {
 
 for ($j=0; $j<5; $j++) {
 $process[$j] = popen('message.php', 'r');
 }

 for ($j=0; $j<5; ++$j) {
 pclose($process[$j]);
 }
}