php man page for sem_acquire

SEM_ACQUIRE(3)								 1							    SEM_ACQUIRE(3)

sem_acquire - Acquire a semaphore

SYNOPSIS
       bool sem_acquire (resource  $sem_identifier)

DESCRIPTION
       sem_acquire(3)  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.

	After processing a request, any semaphores acquired by the process but not explicitly released will be released automatically and a  warn-
       ing will be generated.

PARAMETERS
	      o $sem_identifier
		-$sem_identifier is a semaphore resource, obtained from sem_get(3).

RETURN VALUES
	Returns TRUE on success or FALSE on failure.

SEE ALSO
       sem_get(3), sem_release(3).

PHP Documentation Group 													    SEM_ACQUIRE(3)