How to ensure user singleness when writing files using php

The syntax format is as follows:

flock(resource $handle, int $operation[, int &$wouldblock])

a.$handle: file system pointer, that is, use fopen() Created file resources;

b.$operation: File lock type, which can be one of the following values:

• LOCK_SH acquires a shared lock (reading program);

• LOCK_EX acquires an exclusive lock (writing program);

• LOCK_UN releases Locking (whether shared or exclusive);

• If you do not want flock() to block when locking, you can add the LOCK_NB parameter to $operation (not yet supported on Windows).

c.$wouldblock: Optional parameter, if you want to block other processes when the file is locked, you can set this parameter to 1 or true. (Not supported on Windows).

PS: Using flock() function can not only lock files, but also unlock files.

Example:

<?php
    $file = fopen(&#39;./test.txt&#39;,&#39;w+&#39;);
    if(flock($file, LOCK_EX|LOCK_NB))
    {
     fwrite($file, &#39;PHP中文网&#39;.date(&#39;Y-m-d H:i:s&#39;, time()));
     flock($file, LOCK_UN);
     }else{
     echo "string";
     }
     fclose($file);
?>

Run result:

In the test.txt file中WRITE

PHP中文网2021-03-23 09:09:31

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