PHP realpath_cache_get Function

last modified April 3, 2025

The PHP realpath_cache_get function retrieves the current realpath cache entries. It helps understand how PHP caches resolved file paths.

Basic Definition

The realpath_cache_get function returns an array of cached realpath entries. PHP uses this cache to store resolved paths for better performance.

Syntax: realpath_cache_get(): array. The function takes no parameters and returns an associative array with cache entries.

Basic realpath_cache_get Example

This shows the simplest usage of realpath_cache_get to view cache.

basic_realpath_cache.php

<?php

declare(strict_types=1);

// Access a file to populate the cache
$path = realpath(__FILE__);

// Get the cache contents
$cache = realpath_cache_get();

print_r($cache);

This outputs the realpath cache after resolving the current file's path. The cache contains detailed information about resolved paths.

Cache Entry Structure

Each cache entry contains several fields with information about the path.

cache_structure.php

<?php

declare(strict_types=1);

// Access a file to populate the cache
$path = realpath(__DIR__ . '/../config.ini');

// Get and examine a cache entry
$cache = realpath_cache_get();
$entry = current($cache);

echo "Key: " . key($cache) . "\n";
echo "Resolved path: " . $entry['realpath'] . "\n";
echo "Expire time: " . $entry['expires'] . "\n";
echo "Is directory: " . ($entry['is_dir'] ? 'Yes' : 'No') . "\n";

This shows the structure of a cache entry. Each entry includes the resolved path, expiration time, and whether it's a directory.

Monitoring Cache Size

You can check how many entries are in the realpath cache.

cache_size.php

<?php

declare(strict_types=1);

// Access several files to populate cache
realpath(__FILE__);
realpath(__DIR__);
realpath('/tmp');

// Get cache information
$cache = realpath_cache_get();

echo "Cache contains " . count($cache) . " entries\n";
echo "Memory usage: " . memory_get_usage(true) . " bytes\n";

This demonstrates checking the cache size and memory impact. The cache grows as more paths are resolved during script execution.

Cache Expiration

Cache entries have expiration times based on the realpath_cache_ttl setting.

cache_expiration.php

<?php

declare(strict_types=1);

// Get current time
$now = time();

// Access a file
$path = realpath(__FILE__);

// Check cache expiration
$cache = realpath_cache_get();
$entry = current($cache);

$remaining = $entry['expires'] - $now;
echo "Cache entry expires in $remaining seconds\n";

This calculates how long until a cache entry expires. The default TTL is typically 120 seconds but can be changed in php.ini.

Comparing Cached and Uncached Performance

The cache significantly improves performance for repeated path resolutions.

performance_comparison.php

<?php

declare(strict_types=1);

function timeResolution(string $path): float {
    $start = microtime(true);
    realpath($path);
    return microtime(true) - $start;
}

$path = __FILE__;

// First resolution (uncached)
$uncachedTime = timeResolution($path);

// Second resolution (cached)
$cachedTime = timeResolution($path);

echo "Uncached: " . $uncachedTime . " seconds\n";
echo "Cached: " . $cachedTime . " seconds\n";
echo "Improvement: " . ($uncachedTime/$cachedTime) . "x faster\n";

This compares the performance of cached vs uncached path resolutions. The realpath cache can make repeated operations significantly faster.

Best Practices

Monitor Size: Watch cache size in long-running scripts.
TTL Settings: Adjust realpath_cache_ttl as needed.
Debugging: Use to debug path resolution issues.
Performance: Understand its impact on filesystem ops.

Source

PHP realpath_cache_get Documentation

This tutorial covered the PHP realpath_cache_get function with practical examples showing its usage in different scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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