阻塞模式，程序会一直等待。
<?php
$fp = fopen("lock.txt", "r");
if(flock($fp,LOCK_EX))
{
//code
flock($fp,LOCK_UN);
}
fclose($fp);
?>
非阻塞模式，如果文件被占用直接返回false
<?php
$fp = fopen("lock.txt", "r");
if(flock($fp,LOCK_EX | LOCK_NB))
{
//code
flock($fp,LOCK_UN);
}
else
{
echo "error";
} fclose($fp);
?>
阻塞时设置超时时间
if ($fp = fopen($fileName, 'a')) {
$startTime = microtime();
do {
$canWrite = flock($fp, LOCK_EX);
if (!$canWrite) {
usleep(round(rand(0, 100) * 1000));
}
} while ((!$canWrite) && ((microtime() - $startTime) < 1000));
if ($canWrite) {
fwrite($fp, $dataToSave);
}
fclose($fp);
}