Semaphore Functions
PHP Manual


(PHP 4, PHP 5, PHP 7)

sem_acquireAcquire a semaphore


bool sem_acquire ( resource $sem_identifier [, bool $nowait = false ] )

sem_acquire() by default 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 warning will be generated.



sem_identifier is a semaphore resource, obtained from sem_get().


Specifies if the process shouldn't wait for the semaphore to be acquired. If set to true, the call will return false immediately if a semaphore cannot be immediately acquired.

Return Values

Returns TRUE on success or FALSE on failure.


Version Description
5.6.1 The $nowait parameter was added.

See Also

Semaphore Functions
PHP Manual