08c09-2.php

介绍PHP5的给类型函数应用

<?php
// A function to creating a secondary locking file for us
function lock($filename) {
	// Remove the ability for user aborts until we are finished
	ignore_user_abort(true);

	// Attempt to open, and/or create, the lock file:
	if (!($fp = fopen("{$filename}.lock", 'w'))) {
		die ('ERROR: Could not open file!');
	}

	// Now attempt to get an exclusive lock
	if (!(flock($fp, LOCK_EX))) {
		die('ERROR: Could not get exclusive lock!');
	}
	
	// We now have the lock, return the locked file pointer
	return $fp;
}

// Now create a function that will handle unlocking for us:
function unlock($filepointer) {
	// Unlock the secondary lock file:
	if (!(flock($filepointer, LOCK_UN))) {
		die('ERROR: Could undo exclusive lock!');
	}
	
	// Remove the restriction on user aborts:
	ignore_user_abort(false);
}

// Now use these functions to do a full read/write loop on a file
// incrementing a number for each time the file is written:

// Obtain the lock:
$lock = lock('data.counter');

// Read in the file:
$filedata = @file('data.counter');

// Determine our new count:
$count = isset($filedata[0]) ? $filedata[0] + 1 : 1;

// Now we can write our data:
file_put_contents('data.counter', $count);

// Release the exclusive lock
unlock($lock);

// Now echo out our file contents so that we can see what happened:
echo '<pre>';
readfile('data.counter');
echo '</pre>';
?>