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(PHP 5 >= 5.1.0, PHP 7)

SplFileObject::flockPortable file locking


public SplFileObject::flock ( int $operation [, int &$wouldblock ] ) : bool

Locks or unlocks the file in the same portable way as flock().



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 to not block while locking.


Set to TRUE if the lock would block (EWOULDBLOCK errno condition).

Return Values

Returns TRUE on success or FALSE on failure.


Example #1 SplFileObject::flock() example

= new SplFileObject("/tmp/lock.txt""w");
if (
$file->flock(LOCK_EX)) { // do an exclusive lock
$file->ftruncate(0);     // truncate file
$file->fwrite("Write something here\n");
$file->flock(LOCK_UN);   // release the lock    
} else {
"Couldn't get the lock!";


Version Description
5.5.22, 5.6.6 Added support for the wouldblock parameter on Windows.
5.3.2 The automatic unlocking when the file's resource handle is closed was removed. Unlocking now always has to be done manually.

See Also

  • flock() - Portable advisory file locking

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User Contributed Notes 1 note

digitalprecision at gmail dot com
9 years ago
For the record, the example given here has an explicit command to truncate the file, however with a 'write mode' of 'w', it will do this for you automatically, so the truncate call is not needed.
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