php文件读写锁

$file = fopen("test.txt", $fileOpenMode);
flock($file, $lockMode) or die("Can't lock");
//...
flock($file, LOCK_UN);
fclose($file);

$fileOpenMode："r"（读）；"r+"（写）（不能用"w"，否则由于先打开再加锁，打开后文件内容已经清空了）

$lockMode：LOCK_SH（读）；LOCK_EX（写）

<?php
sleep(3);
return;
$mode = $_GET['mode'];
switch($mode){
case "r":
    $fileOpenMode = "r";
    $lockMode = LOCK_SH;
    $sleepTime = 3;
    break;
case "w":
    $fileOpenMode = "r+";
    $lockMode = LOCK_EX;
    $sleepTime = 5;
    break;
}

echo "QueryTime:" . time() . "<br>";
$startTime = time();
echo "Mode:" . $mode . "<br>";
$file = fopen("test.txt", $fileOpenMode);
flock($file, $lockMode) or die("Can't lock");
sleep($sleepTime);
switch($mode){
case "r":
    echo "Data:" . fgets($file) . "<br>";
    break;
case "w":
    echo "Data:" . "(Written)" . "<br>";
    fputs($file, "Write data info file at " . time());
    break;
}
flock($file, LOCK_UN);
fclose($file);
echo "Time:" . (time()-$startTime) . "<br>";
echo "Now:" . time() . "<br>";
?>