php-pcntlHow to use pcntl_waitpid in PHP?

PCNTL_WAITPID is a PHP function used to wait for a child process to terminate. It takes two parameters, the first being the PID of the process to wait for, and the second being a variable to store the status of the child process.

<?php
$pid = pcntl_fork();
if ($pid == -1) {
    die('could not fork');
} else if ($pid) {
    // parent
    $status = null;
    pcntl_waitpid($pid, $status);
} else {
    // child
    exit();
}

The output of the above code will be nothing, as the child process exits immediately.

Code explanation

1. pcntl_fork() - This function creates a child process.
2. pcntl_waitpid($pid, $status) - This function waits for the child process to terminate, and stores the status of the child process in the second parameter.
3. exit() - This function exits the child process.

Helpful links

• PHP pcntl_waitpid Manual
• PHP pcntl_fork Manual

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