PHP flock() 函数
定义和用法
flock() 函数锁定或释放文件。
若成功，则返回 true。若失败，则返回 false。
语法
flock(file,lock,block)
| 参数 | 描述 |
|---|---|
| file | 必需。规定要锁定或释放的已打开的文件。 |
| lock | 必需。规定要使用哪种锁定类型。 |
| block | 可选。若设置为 1 或 true，则当进行锁定时阻挡其他进程。 |
Description
The operation of file Must be an already opened file pointer.
lock The parameter can be one of the following values:
- To obtain a shared lock (reading program), set lock to LOCK_SH (set to 1 in versions before PHP 4.0.1).
- To obtain an exclusive lock (writing program), set lock to LOCK_EX (set to 2 in versions before PHP 4.0.1).
- To release the lock (whether shared or exclusive), set lock to LOCK_UN (set to 3 in versions before PHP 4.0.1).
- If you do not want flock() to block during locking, then set lock Add LOCK_NB (set to 4 in versions before PHP 4.0.1).
Tips and Comments
Tip:Can be done by fclose() To release the locking operation, the code will also automatically call when the code execution is completed.
Comment:Since flock() requires a file pointer, it may be necessary to use a special locking file to protect access to files intended to be opened in write mode (add "w" or "w+" in the fopen() function).
Example
<?php
$file = fopen("test.txt","w+");
// exclusive lock
if (flock($file,LOCK_EX))
{
fwrite($file,"Write something");
// release lock
flock($file,LOCK_UN);
}
else
{
echo "Error locking file!";
}
fclose($file);
?>
