(PHP 3 >= 3.0.6, PHP 4, PHP 5)
sem_acquire -- Acquire a semaphore
Description
bool 
sem_acquire ( resource sem_identifier )
     sem_acquire() blocks (if necessary) until the
     semaphore can be acquired.  A process attempting to acquire a
     semaphore which it has already acquired will block forever
     if acquiring the semaphore would cause its maximum number
     of semaphore to be exceeded.
     sem_identifier is a semaphore ressource,
     obtained from sem_get().
    
     Returns TRUE on success or FALSE on failure.
    
     After processing a request, any semaphores acquired by the
     process but not explicitly released will be released automatically
     and a warning will be generated.
    
 
     See also
     sem_get(), and
     sem_release().