08c09-3.php

介绍PHP5的给类型函数应用

<?php
// A function to creating a lock directory for us, getting around
// the need to use flock()
function lock($filename) {
	// Remove the ability for user aborts until we are finished
	ignore_user_abort(true);

	// Start a counter, we only want to try to obtain a lock
	// a certain number of times:
	$counter = 0;
	
	// Until we get a lock, or die trying, go for it:
	do {
		// Sleep for counter-squared seconds, longer each time:
		sleep($counter * $counter);
		
		// Make the directory:
		$success = @mkdir("{$filename}.dirlock");
	}
	while ( !($success) &&  ($counter++ < 10) );
	
	// If counter is 11, then we never got the lock:
	if ($counter == 11) {
		die('ERROR: Could not get exclusive lock!');
	}

	// Otherwise we now have the lock and are done!
}

// Now create a function that will handle unlocking for us:
function unlock($filename) {
	// Remove the directory:
	if (!(rmdir("{$filename}.dirlock"))) {
		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 the file, determine our count, and write the data:
$filedata = @file('data.counter');
$count = isset($filedata[0]) ? $filedata[0] + 1 : 1;
file_put_contents('data.counter', $count);

// Release the exclusive lock
unlock('data.counter');

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