A single-file counter that survives concurrent increments correctly using flock + read-modify-write inside the locked region. Useful for crude visitor or job-id counters when you don't want a DB.
PHP
<?php
function increment(string $file, int $by = 1): int {
$fh = fopen($file, 'c+');
flock($fh, LOCK_EX);
$current = (int)stream_get_contents($fh);
$next = $current + $by;
rewind($fh);
ftruncate($fh, 0);
fwrite($fh, (string)$next);
fflush($fh);
flock($fh, LOCK_UN);
fclose($fh);
return $next;
}
$jobId = increment('/var/lib/myapp/jobs.counter');
echo "Assigned job #$jobId\n";Save your own code snippets
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