php man page for dio_fcntl

DIO_FCNTL(3)								 1							      DIO_FCNTL(3)

dio_fcntl - Performs a c library fcntl on fd

SYNOPSIS
       mixed dio_fcntl (resource  $fd, int  $cmd, [mixed  $args])

DESCRIPTION
	The  dio_fcntl(3) function performs the operation specified by $cmd on the file descriptor $fd. Some commands require additional arguments
       $args to be supplied.

PARAMETERS
	      o $fd
		- The file descriptor returned by dio_open(3).

	      o $cmd
		- Can be one of the following operations:

		     o F_SETLK - Lock is set or cleared. If the lock is held by someone else dio_fcntl(3) returns -1.

		     o F_SETLKW - like F_SETLK, but in case the lock is held by someone else, dio_fcntl(3) waits until the lock is released.

		     o F_GETLK - dio_fcntl(3) returns an associative array (as described above) if someone else prevents  lock.  If  there  is	no
		       obstruction key "type" will set to F_UNLCK.

		     o F_DUPFD - finds the lowest numbered available file descriptor greater than or equal to $args and returns them.

		     o F_SETFL - Sets the file descriptors flags to the value specified by $args, which can be O_APPEND, O_NONBLOCK or O_ASYNC. To
		       use O_ASYNC you will need to use the PCNTL extension.

	      o $args
		-$args is an associative array, when $cmd is F_SETLK or F_SETLLW, with the following keys:

		     o start - offset where lock begins

		     o length - size of locked area. zero means to end of file

		     o whence - Where l_start is relative to: can be SEEK_SET, SEEK_END and SEEK_CUR

		     o type - type of lock: can be F_RDLCK (read lock), F_WRLCK (write lock) or F_UNLCK (unlock)

RETURN VALUES
	Returns the result of the C call.

EXAMPLES
       Example #1

	      Setting and clearing a lock

	      <?php

	      $fd = dio_open('/dev/ttyS0', O_RDWR);

	      if (dio_fcntl($fd, F_SETLK, Array("type"=>F_WRLCK)) == -1) {
		 // the file descriptor appears locked
		 echo "The lock can not be cleared. It is held by someone else.";
	      } else {
		 echo "Lock successfully set/cleared";
	      }

	      dio_close($fd);
	      ?>

NOTES
       Note

	      This function is not implemented on Windows platforms.

PHP Documentation Group 													      DIO_FCNTL(3)