堵塞写入代码：（全部程序会等待上次程序运行结束才会运行，30秒会超时）
<?php
$file = fopen("test.txt","w+"); $t1 = microtime(TRUE);
if (flock($file,LOCK_EX))
{
sleep(10);
fwrite($file,"Write something");
flock($file,LOCK_UN);
echo "Ok locking file!";
}
else
{
echo "Error locking file!";
} fclose($file); $t2 = microtime(TRUE);
echo sprintf("%.6f",($t2-$t1));
非堵塞写入代码：（仅仅要文件被占用，则显示Error locking file!）
<? php
$file = fopen("test.txt","a+"); $t1 = microtime(TRUE);
if (flock($file,LOCK_EX|LOCK_NB))
{
sleep(10);
fwrite($file,"Write something");
flock($file,LOCK_UN);
echo "Ok locking file!";
}
else
{
echo "Error locking file!";
} fclose($file); $t2 = microtime(TRUE);
echo sprintf("%.6f",($t2-$t1));
