PHP TutorialCompile PHP ExtensionsContributing to the PHP CoreContributing to the PHP ManualCreate PDF files in PHPInstalling a PHP environment on WindowsPHP Alternative Syntax for Control StructuresPHP APCuPHP Array iterationPHP ArraysPHP Asynchronous programmingPHP Autoloading PrimerPHP BC Math (Binary Calculator)PHP Built in serverPHP CachePHP Classes and ObjectsPHP ClosurePHP Coding ConventionsPHP Command Line Interface (CLI)PHP CommentsPHP Common ErrorsPHP Compilation of Errors and WarningsPHP Composer Dependency ManagerPHP ConstantsPHP Control StructuresPHP CookiesPHP CryptographyPHP DateTime ClassPHP DebuggingPHP Dependency InjectionPHP Design PatternsPHP Docker deploymentPHP Exception Handling and Error ReportingPHP Executing Upon an ArrayPHP File handlingPHP Filters & Filter FunctionsPHP Functional ProgrammingPHP FunctionsPHP GeneratorsPHP Headers ManipulationPHP How to break down an URLPHP How to Detect Client IP AddressPHP HTTP AuthenticationPHP Image Processing with GDPHP ImagickPHP IMAPPHP Installing on Linux/Unix EnvironmentsPHP JSONPHP LocalizationPHP LoopsPHP Machine learningPHP Magic ConstantsPHP Magic MethodsPHP Manipulating an ArrayPHP mongo-phpPHP Multi Threading ExtensionPHP MultiprocessingPHP MySQLiPHP MySQLi affected rows returns 0 when it should return a positive integerPHP NamespacesPHP Object SerializationPHP OperatorsPHP Output BufferingPHP Outputting the Value of a VariablePHP Parsing HTMLPHP Password Hashing FunctionsPHP PDOPHP PerformancePHP PHPDocPHP Processing Multiple Arrays TogetherPHP PSRPHP Reading Request DataPHP RecipesPHP ReferencesPHP ReflectionPHP Regular Expressions (regexp/PCRE)PHP Secure Remeber MePHP SecurityPHP Sending EmailPHP SerializationPHP SessionsPHP SimpleXMLPHP SOAP ClientPHP SOAP ServerPHP SocketsPHP SPL data structuresPHP SQLite3PHP StreamsPHP String formattingPHP String Parsing

PHP Multiprocessing

From WikiOD

Multiprocessing using built-in fork functions[edit | edit source]

You can use built-in functions to run PHP processes as forks. This is the most simple way to achieve parallel work if you don't need your threads to talk to each other.

This allows you to put time intensive tasks (like uploading a file to another server or sending an email) to another thread so your script loads faster and can use multiple cores but be aware that this is not real multithreading and your main thread won't know what the children are up to.

Note that under Windows this will make another command prompt pop up for each fork you start.


$cmd = "php worker.php 10";
if(strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') // for windows use popen and pclose
else //for unix systems use shell exec with "&" in the end
    exec('bash -c "exec nohup setsid '.$cmd.' > /dev/null 2>&1 &"');


//send emails, upload files, analyze logs, etc
$sleeptime = $argv[1];

Creating child process using fork[edit | edit source]

PHP has built in function pcntl_fork for creating child process. pcntl_fork is same as fork in unix. It does not take in any parameters and returns integer which can be used to differentiate between parent and child process. Consider the following code for explanation

    // $pid is the PID of child
    $pid = pcntl_fork();
    if ($pid == -1) {
         die('Error while creating child process');
    } else if ($pid) {
         // Parent process
    } else {
         // Child process

As you can see -1 is an error in fork and the child was not created. On creation of child, we have two processes running with separate PID.

Another consideration here is a zombie process or defunct process when parent process finishes before child process. To prevent a zombie children process simply add pcntl_wait($status) at the end of parent process.

pnctl_wait suspends execution of parent process until the child process has exited.

It is also worth noting that zombie process can't be killed using SIGKILL signal.

Inter-Process Communication[edit | edit source]

Interprocess communication allows programmers to communicate between different processes. For example let us consider we need to write an PHP application that can run bash commands and print the output. We will be using proc_open , which will execute the command and return a resource that we can communicate with. The following code shows a basic implementation that runs pwd in bash from php

    $descriptor = array(
        0 => array("pipe", "r"), // pipe for stdin of child
        1 => array("pipe", "w"), // pipe for stdout of child
    $process = proc_open("bash", $descriptor, $pipes);
    if (is_resource($process)) {
        fwrite($pipes[0], "pwd" . "\n");
        echo stream_get_contents($pipes[1]);
        $return_value = proc_close($process);


proc_open runs bash command with $descriptor as descriptor specifications. After that we use is_resource to validate the process. Once done we can start interacting with the child process using $pipes which is generated according to descriptor specifications.

After that we can simply use fwrite to write to stdin of child process. In this case pwd followed by carriage return. Finally stream_get_contents is used to read stdout of child process.

Always remember to close the child process by using proc_close() which will terminate the child and return the exit status code.