Programming PHP

Name

flock

Synopsis

bool flock(int handle, int operation[, int would_block])

Attempts to lock the file path of the file specified by handle. The operation is one of the following values:

LOCK_SH	Shared lock (reader)
LOCK_EX	Exclusive lock (writer)
LOCK_UN	Release a lock (either shared or exclusive)
LOCK_NB	Add to LOCK_SH or LOCK_EX to obtain a non-blocking lock

If specified, would_block is set to true if the operation would cause a block on the file. The function returns false if the lock could not be obtained, and true if the operation succeeded.

Because file locking is implemented at the process level on most systems, flock( ) cannot prevent two PHP scripts running in the same web server process from accessing a file at the same time.