Two points worth noting:
1. fsync() is not suitable for high throughput, use it only when the durability of a file write really matters to you.
2. fsync() includes an implicit call to fflush() so you don't need to manually flush before you sync.
(PHP 8 >= 8.1.0)
fsync — Synchronizes changes to the file (including meta-data)
$stream): boolThis function synchronizes changes to the file, including its meta-data. This is similar to fflush(), but it also instructs the operating system to write to the storage media.
streamO ponteiro de arquivo precisa ser válido, e apontar para um arquivo aberto por fopen() ou fsockopen() (e ainda não fechado por fclose()).
Retorna true em caso de sucesso ou false em caso de falha.
Exemplo #1 fsync() example
<?php
$file = 'test.txt';
$stream = fopen($file, 'w');
fwrite($stream, 'test data');
fwrite($stream, "\r\n");
fwrite($stream, 'additional data');
fsync($stream);
fclose($stream);
?>
Two points worth noting:
1. fsync() is not suitable for high throughput, use it only when the durability of a file write really matters to you.
2. fsync() includes an implicit call to fflush() so you don't need to manually flush before you sync.