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 byfclose()(will be called automatically after the script ends), now you need to manually unlock

operation

1.LOCK_SHObtain shared lock (reading program)

2.LOCK_EXObtain exclusive lock (writing program)

3.LOCK_UNRelease the lock (whether shared or exclusive)

4.LOCK_NBNot locked when flock() Blocking

Example 1: A uses an exclusive lock to write the file, B reads the file, blocking

a.php

b.php

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

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

b.php

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

b.php

Execute a.php first, then b.php

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 lock

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.

Using exclusive lock

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.

This article explains the usage examples of php flock. For more related content, please pay attention to the php Chinese website.

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!