The flock() function locks or releases a file.
This function returns TRUE on success or FALSE on failure.
|file||Required. Specifies an open file to lock or release|
|lock||Required. Specifies what kind of lock to use.
|block||Optional. Set to 1 to block other processes while locking|
Note: These locks only apply to the current PHP process. Other processes can modify or delete a PHP-locked file if permissions allow.
Note: flock() is mandatory under Windows.
Tip: The lock is released also by fclose(), which is called automatically when script is finished.