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 deve ser válido e deve apontar para um arquivo aberto com sucesso 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.