PHP filesize Function

last modified April 3, 2025

The PHP filesize function returns the size of a file in bytes. It's useful for checking file sizes before processing or displaying them.

Basic Definition

The filesize function returns the size of the specified file. It takes one parameter: the filename or path to the file.

Syntax: filesize(string $filename): int|false. Returns file size in bytes or false on failure. The result is cached; use clearstatcache() for updated results.

Basic filesize Example

This shows the simplest usage of filesize to get a file's size.

basic_filesize.php

<?php

declare(strict_types=1);

$filename = "example.txt";
$size = filesize($filename);

echo "File size: $size bytes"; // Outputs size in bytes

This gets the size of "example.txt" in bytes. The function requires the file to exist and be accessible to work properly.

Formatting File Size

We can format the raw byte count into a human-readable format.

format_size.php

<?php

declare(strict_types=1);

function formatSize(int $bytes): string {
    $units = ['B', 'KB', 'MB', 'GB', 'TB'];
    $index = 0;
    
    while ($bytes >= 1024 && $index < 4) {
        $bytes /= 1024;
        $index++;
    }
    
    return round($bytes, 2) . ' ' . $units[$index];
}

$filename = "largefile.zip";
$size = filesize($filename);

echo "File size: " . formatSize($size);

This converts bytes to appropriate units (KB, MB, etc.). The function handles files of any size by dynamically selecting the best unit.

Checking File Existence

It's good practice to check if a file exists before getting its size.

check_existence.php

<?php

declare(strict_types=1);

$filename = "nonexistent.txt";

if (file_exists($filename)) {
    $size = filesize($filename);
    echo "File size: $size bytes";
} else {
    echo "File does not exist";
}

This prevents errors when trying to get the size of non-existent files. Always verify file existence before operations to avoid warnings.

Remote File Size

For remote files, we need a different approach as filesize doesn't work with HTTP URLs.

remote_file.php

<?php

declare(strict_types=1);

function getRemoteFileSize(string $url): ?int {
    $headers = get_headers($url, true);
    
    if ($headers && isset($headers['Content-Length'])) {
        return (int)$headers['Content-Length'];
    }
    
    return null;
}

$fileUrl = "https://example.com/largefile.pdf";
$size = getRemoteFileSize($fileUrl);

echo $size ? "Remote file size: $size bytes" : "Size unavailable";

This uses HTTP headers to get remote file sizes. Note that not all servers provide Content-Length headers for all files.

Directory Size Calculation

We can calculate total size of all files in a directory recursively.

directory_size.php

<?php

declare(strict_types=1);

function getDirectorySize(string $path): int {
    $size = 0;
    $files = new RecursiveIteratorIterator(
        new RecursiveDirectoryIterator($path)
    );
    
    foreach ($files as $file) {
        if ($file->isFile()) {
            $size += $file->getSize();
        }
    }
    
    return $size;
}

$dir = "/path/to/directory";
$totalSize = getDirectorySize($dir);

echo "Directory size: " . formatSize($totalSize);

This recursively calculates the total size of all files in a directory. It uses PHP's SPL iterators for efficient directory traversal.

Best Practices

Error Handling: Always check if files exist and are readable.
Caching: Use clearstatcache() if file sizes might change.
Memory: Be careful with very large files on 32-bit systems.
Permissions: Ensure proper file permissions for access.

Source

PHP filesize Documentation

This tutorial covered the PHP filesize 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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