PHP function flock()

Availability in PHP 4.0

Portable advisory file locking

Parameters

Parameter	Data type	Default value	Note
$handle	resource	not	An open file pointer.
$operation	int	not	operation is one of the following: LOCK_SH to acquire a shared lock (reader). @param int $wouldblock [optional] The optional third argument is set to true if the lock would block (EWOULDBLOCK errno condition).
$wouldblock	int	null	The optional third argument is set to true if the lock would block (EWOULDBLOCK errno condition).

Return values

bool

Returns true on success, otherwise false on failure.

Other resources

Official documentation for the flock function