<?php
    class ForkMaster()
    {
        private $up_to;

        public function ForkMaster()
        {
            $this->up_to = 0;
        }

        public function countToOneThousand()
        {
            $pid = pcntl_fork();

            if($pid < 0)
                throw new Exception('No fork for you!');

            else if(!$pid)
            {
                //THIS IS THE CHILD PROCESS
                for($i = 1;$i <= 1000;$i++)
                    $this->up_to = $i;
            }

            else if($pid)
            {
                //THIS IS THE PARENT PROCESS
                while($this->up_to < 1000)
                    echo($this->up_to."\n");
            }
        }
    }

    $mast = new ForkMaster();
    $mast->countToOneThousand();