PHP clearstatcache() Function: Usage and Examples

Clears cached filesystem stat information so a subsequent check can observe recent changes.

What It Does and When to Use It

Refresh stat and realpath caches for a specific file. APCu stores local application data, Redis is external and can be shared among hosts, and OPcache stores compiled code.

Requirements, Inputs and Expected Behavior

Confirm the runtime, extension, environment variables, and permissions before running the examples in production. The stat cache and PHP realpath cache are distinct; use the clear_realpath_cache flag when appropriate.

Example 1: Basic Operation

Refresh stat and realpath caches for a specific file.

<?php
$path = __FILE__;
 $sizeBefore = filesize($path);
 clearstatcache(true, $path);
 $sizeAfter = filesize($path);
 echo "$sizeBefore -> $sizeAfter";

Example 2: Behavior and Validation

Check metadata after another process may have modified a file.

<?php
$path = __DIR__ . '/report.csv';
 clearstatcache(false, $path);
 if (is_file($path)) echo filemtime($path);

Practical Example: Application Use

Use a temporary fixture to observe a metadata change.

<?php
$file = tempnam(sys_get_temp_dir(), 'stat-');
 file_put_contents($file, 'one');
 $a = filesize($file);
 file_put_contents($file, 'updated content');
 clearstatcache(false, $file);
 $b = filesize($file);
 unlink($file);
 echo "$a to $b";

Important Behavior and Edge Cases

The second example highlights: Check metadata after another process may have modified a file. The practical example adds: Use a temporary fixture to observe a metadata change.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Clears cached filesystem stat information so a subsequent check can observe recent changes.
• Use a temporary fixture to observe a metadata change.
• Define TTL, invalidation, and concurrency behavior separately from the cache storage API.