PHP realpath_cache_size Function

last modified April 3, 2025

The PHP realpath_cache_size function manages the realpath cache which stores resolved path information. This cache improves performance by avoiding repeated filesystem lookups.

Basic Definition

The realpath_cache_size function returns or sets the size of the realpath cache. This cache stores resolved file paths to avoid repeated filesystem operations.

Syntax: realpath_cache_size(): int. The function returns the current size of the realpath cache in bytes. It can be configured in php.ini.

Checking Current Cache Size

This example shows how to check the current size of the realpath cache.

check_cache_size.php

<?php

declare(strict_types=1);

$cacheSize = realpath_cache_size();

echo "Current realpath cache size: " . $cacheSize . " bytes\n";

This outputs the current size of the realpath cache in bytes. The default is typically 16K, but can vary based on PHP configuration.

Monitoring Cache Usage

This example demonstrates how to monitor cache usage during script execution.

monitor_cache.php

<?php

declare(strict_types=1);

function checkCache(): void {
    echo "Cache size: " . realpath_cache_size() . " bytes\n";
}

checkCache();

// Perform some filesystem operations
file_exists(__FILE__);
is_dir(__DIR__);

checkCache();

This shows how the cache size might increase after filesystem operations. The cache grows as more paths are resolved and stored.

Comparing Cache Before/After Operations

This example compares cache size before and after resolving multiple paths.

compare_cache.php

<?php

declare(strict_types=1);

$initialSize = realpath_cache_size();
echo "Initial cache size: $initialSize bytes\n";

// Resolve multiple paths
for ($i = 0; $i < 100; $i++) {
    realpath(__FILE__);
}

$finalSize = realpath_cache_size();
echo "Final cache size: $finalSize bytes\n";
echo "Cache growth: " . ($finalSize - $initialSize) . " bytes\n";

This demonstrates how resolving paths increases the cache size. The growth depends on the number of unique paths resolved.

Cache Size with Different Path Types

This example shows how different path types affect the cache size differently.

path_types_cache.php

<?php

declare(strict_types=1);

$startSize = realpath_cache_size();

// Resolve different types of paths
realpath('/');
realpath('/tmp');
realpath(__FILE__);
realpath(__DIR__ . '/../');

$endSize = realpath_cache_size();

echo "Cache increased by: " . ($endSize - $startSize) . " bytes\n";

Different path types (root, temp, current file, parent directory) consume varying amounts of cache space. Longer paths typically use more cache.

Realpath Cache Info

This example combines realpath_cache_size with realpath_cache_get for detailed cache information.

cache_info.php

<?php

declare(strict_types=1);

// Ensure some paths are cached
realpath(__FILE__);
realpath(__DIR__);

$cacheSize = realpath_cache_size();
$cacheInfo = realpath_cache_get();

echo "Cache size: $cacheSize bytes\n";
echo "Cached entries: " . count($cacheInfo) . "\n";
echo "First entry key: " . array_key_first($cacheInfo) . "\n";

This shows the relationship between cache size and number of entries. Each cached path consumes memory based on its length and associated data.

Best Practices

Monitor Usage: Check cache size in performance-critical apps.
Adjust Size: Increase cache size if resolving many paths.
TTL Awareness: Understand cached paths expire after realpath_cache_ttl.
Performance: Larger caches improve performance but use more memory.

Source

PHP realpath_cache_size Documentation

This tutorial covered the PHP realpath_cache_size 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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