semaphore.php

<?php
$id=1; 
$shared1 = shm_attach(1); 
$sem = sem_get(1,1); 
shm_put_var($shared1,1,$id); 
shm_put_var($shared1,2,$sem); 
$pid = pcntl_fork(); 

if ($pid == -1) { 
  die('could not fork'); 
} else if (!$pid) { 
  while(true){ 
    $s1 = shm_attach(1); 
    sem_acquire($sem); 
    $idx = shm_get_var($s1,1); 
    print "P1: hello (".($idx++).") "; 
    shm_put_var($s1,1,$idx); 
    sem_release($sem); 
    usleep(25600); 
  } 
} 

sleep(1); 

$pid2 = pcntl_fork(); 

if($pid2 == -1){ 
  die('could not fork'); 
}else if(!$pid2){ 
  while(true){ 
    $s1 = shm_attach(1); 
    sem_acquire($sem); 
    $idx = shm_get_var($s1,1); 
    print "P2: hello (".($idx++).") "; 
    shm_put_var($s1,1,$idx); 
    sem_release($sem); 
    usleep(25600); 
  } 
} 

if($pid || $pid2){ 
  pcntl_wait($status); 
}
?>