(PHP 5, PHP 7)
streamWrapper::stream_lock — Advisory file locking
public streamWrapper::stream_lock ( int $operation ) : bool
This method is called in response to flock(), when file_put_contents() (when flags contains LOCK_EX), stream_set_blocking() and when closing the stream (LOCK_UN).
operation
operation is one of the following:
LOCK_SH to acquire a shared lock (reader). LOCK_EX to acquire an exclusive lock (writer). LOCK_UN to release a lock (shared or exclusive). LOCK_NB if you don't want flock() to block while locking. (not supported on Windows) Returns true on success or false on failure.
Emits E_WARNING if call to this method fails (i.e. not implemented).
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https://www.php.net/manual/en/streamwrapper.stream-lock.php