Description
int 
pcntl_fork ( void  )
    The pcntl_fork() function creates a child
    process that differs from the parent process only in its PID and
    PPID. Please see your system's fork(2) man page for specific details as to
    how fork works on your system.
   
    On success, the PID of the child process is returned in the
    parent's thread of execution, and a 0 is returned in the child's
    thread of execution.  On failure, a -1 will be returned in the
    parent's context, no child process will be created, and a PHP
    error is raised.
   
Example 1. pcntl_fork() example 
<?php
  $pid = pcntl_fork(); if ($pid == -1) {      die('could not fork'); } else if ($pid) {      // we are the parent      pcntl_wait($status); //Protect against Zombie children } else {      // we are the child }
  ?>
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  | 
    See also pcntl_waitpid() and
    pcntl_signal().