Description
bool flock (int fp, int operation [, int
wouldblock])
PHP supports a portable way of locking complete files in an
advisory way (which means all accessing programs have to use the
same way of locking or it will not work).
flock() operates on fp
which must be an open file
pointer. operation is one of the following
values:
To acquire a shared lock (reader), set
operation to LOCK_SH (set to 1 prior to
PHP 4.0.1).
To acquire an exclusive lock (writer), set
operation to LOCK_EX (set to 2 prior to
PHP 4.0.1).
To release a lock (shared or exclusive), set
operation to LOCK_UN (set to 3 prior to
PHP 4.0.1).
If you don't want flock() to block while
locking, add LOCK_NB (4 prior to PHP 4.0.1) to
operation.
Flock() allows you to perform a simple
reader/writer model which can be used on virtually every platform
(including most Unices and even Windows). The optional 3rd
argument is set to true if the lock would block (EWOULDBLOCK
errno condition)
Flock() returns true on success and false on
error (e.g. when a lock could not be acquired).
| Warning |
On most operation systems flock() is implemented
at the process level. When using a multithreaded server API like
ISAPI you cannot rely on flock() to protect
files against other PHP scripts running in parallel threads of the
same server instance!
|
Manual: flock
