<?php
for ($i = 1; $i <= 5; $i++) {
        $pid = pcntl_fork();
        if (!$pid) {
                print "In child $i\n";
                exit($i);
        }
}
while (pcntl_waitpid(0, $status) != -1) {
        $status = pcntl_wexitstatus($status);
        echo "Child $status completed\n";
}
 

In child 4
Child 4 completed
In child 1
Child 1 completed
In child 2
Child 2 completed
In child 3
Child 3 completed
In child 5
Child 5 completed