An explanation of php flock usage examples
- jackloveOriginal
- 2018-06-09 11:04:432695browse
php flock usage example
bool flock ( resource $handle , int $operation [, int &$wouldblock ] )
flock()Allows the execution of a simple function that can be used on any platform Read/write model (including most Unix derivatives and windows)
Prior to PHP 5.3.2, the lock will be released by fclose() (will be called automatically after the script ends), now you need to manually unlock
operation
1. LOCK_SH Obtain shared lock (reading program)
2.LOCK_EX Obtain exclusive lock (writing program)
3.LOCK_UN Release the lock (whether shared or exclusive)
4.LOCK_NB Not locked when flock() Blocking
Example 1: A uses an exclusive lock to write the file, B reads the file, blocking
a.php
<?php
$file = 'test.txt';
$fp = fopen($file, 'w');
if(flock($fp, LOCK_EX)){ // 取得独占锁
fwrite($fp, "Hello World\r\n"); // 写入数据
sleep(10); // sleep 10秒，文件被锁定
fwrite($fp, "Hello PHP\r\n"); // 写入数据
flock($fp, LOCK_UN); // 解锁
}
fclose($fp);
?>b.php
<?php
$file = 'test.txt';
$fp = fopen($file, 'r');
if(flock($fp, LOCK_SH)){ // 取得贡献锁
while(!feof($fp)){
echo fread($fp, 100);
}
flock($fp, LOCK_UN);
}
fclose($fp);
?>Execute a first .php, and then execute b.php
a to obtain the exclusive lock, b can only wait until a is executed and the lock is released before b can be executed, Blocking
Example 2: A and B both use shared locks and do not block
a.php
<?php
$file = 'test.txt';
$fp = fopen($file, 'r');
if(flock($fp, LOCK_SH)){ // 取得共享锁
sleep(10); // sleep 10秒
while(!feof($fp)){
echo fread($fp, 100);
}
flock($fp, LOCK_UN);
}
fclose($fp);
?>b.php
6881d79e58a19bf081508955ca08811c
Execute a first .php, and then execute b.php
b can output the file content without waiting for a to finish executing, non-blocking
Example 3: Both A and B use exclusive locks to write files, blocking
## a.php
<?php
$file = 'test.txt';
$fp = fopen($file, 'a');
if(flock($fp, LOCK_EX)){ // 取得独占锁
fwrite($fp, "Hello World\r\n"); // 写入数据
sleep(10); // sleep 10秒，文件被锁定
fwrite($fp, "Hello PHP\r\n"); // 写入数据
flock($fp, LOCK_UN); // 解锁
}
fclose($fp);
?>
b.php
<?php
$file = 'test.txt';
$fp = fopen($file, 'a');
if(flock($fp, LOCK_EX)){ // 取得独占锁
fwrite($fp, "How Are You\r\n"); // 写入数据
fwrite($fp, "Show Me The Money\r\n"); // 写入数据
flock($fp, LOCK_UN); // 解锁
}
fclose($fp);
?>
Execute a.php first, Then execute b.php
b needs to wait for a to be executed before writing data, blocking
Example 4: LOCK_NB does not block or wait when locked
##a.php<?php
$file = 'test.txt';
$fp = fopen($file, 'a');
if(flock($fp, LOCK_EX)){ // 取得独占锁
fwrite($fp, "Hello World\r\n"); // 写入数据
sleep(10); // sleep 10秒，文件被锁定
fwrite($fp, "Hello PHP\r\n"); // 写入数据
flock($fp, LOCK_UN); // 解锁
}
fclose($fp);
?>
b.php<?php
$file = 'test.txt';
$fp = fopen($file, 'a');
if(flock($fp, LOCK_EX|LOCK_NB)){ // 取得独占锁
fwrite($fp, "How Are You\r\n"); // 写入数据
fwrite($fp, "Show Me The Money\r\n"); // 写入数据
flock($fp, LOCK_UN); // 解锁
}else{
echo 'file locked';
}
fclose($fp);
?>
b cannot obtain the exclusive lock. There is no need to wait for a to complete execution, but directly returns the prompt that the lock cannot be obtained.
Non-blocking
Summary:
Use shared lockLOCK_SH. If it is reading, there is no need to wait, but if it is writing Enter, need to wait for the read to complete.
Using exclusive lockLOCK_EX, both writing/reading need to wait.
LOCK_UN, regardless of whether a shared/read lock is used, it needs to be unlocked after use.
LOCK_NB, when locked, does not block, but prompts for lock.
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