An explanation of php flock usage examples
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
<?php
$file = 'test.txt';
$fp = fopen($file, 'r');
if(flock($fp, LOCK_SH)){ // 取得共享锁
while(!feof($fp)){
echo fread($fp, 100);
}
flock($fp, LOCK_UN);
}
fclose($fp);
?>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 Non-blocking Summary: LOCK_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. LOCK_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. Related recommendations: php str_replace Explanation of the method of replacing a specified number of times About header, headers_sent, headers_list, header_remove usage instructions Solution to change the integer type of field returned by mysql through PDO to String type The above is the detailed content of An explanation of php flock usage examples. For more information, please follow other related articles on the PHP Chinese website!<?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);
?>
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