PHP dirname Function

last modified April 3, 2025

The PHP dirname function extracts the directory path component from a full path string. It's essential for working with file system paths.

Basic Definition

The dirname function returns the parent directory's path of the given path. It takes two parameters: the path string and an optional levels.

Syntax: dirname(string $path, int $levels = 1): string. The function is binary-safe and works with both Unix and Windows paths.

Basic dirname Example

This shows the simplest usage of dirname to extract a directory.

basic_dirname.php

<?php

declare(strict_types=1);

$path = "/var/www/html/index.php";
$directory = dirname($path);

echo $directory; // Outputs: /var/www/html

This extracts "/var/www/html" from the full path. The function returns the parent directory of the given file path.

Multiple Levels Example

The second parameter can traverse multiple directory levels up.

dirname_levels.php

<?php

declare(strict_types=1);

$path = "/var/www/html/index.php";
$directory = dirname($path, 2);

echo $directory; // Outputs: /var

Here we go up two directory levels from the file path. The levels parameter controls how many parent directories to traverse upwards.

Windows Path Example

dirname works with Windows paths using backslashes.

windows_path.php

<?php

declare(strict_types=1);

$path = "C:\\Windows\\System32\\kernel32.dll";
$directory = dirname($path);

echo $directory; // Outputs: C:\Windows\System32

The function correctly handles Windows-style paths. It returns the parent directory of the given file path.

URL Path Example

dirname can also extract the directory from URLs.

url_path.php

<?php

declare(strict_types=1);

$url = "https://example.com/images/logo.png";
$directory = dirname($url);

echo $directory; // Outputs: https://example.com/images

This extracts the directory portion from the URL. Note that dirname doesn't validate URLs - it processes them as strings.

Edge Cases

dirname has specific behaviors with edge cases worth noting.

edge_cases.php

<?php

declare(strict_types=1);

$path1 = "/var/www/html/";
$path2 = "/var/www/html";
$path3 = "filename.txt";

echo dirname($path1); // Outputs: /var/www
echo dirname($path2); // Outputs: /var/www
echo dirname($path3); // Outputs: .

With directory paths, it returns the parent directory. For simple filenames, it returns ".". Trailing slashes don't affect the result.

Best Practices

Path Validation: Verify paths exist before processing.
Levels Parameter: Use carefully to avoid going too far up.
Security: Sanitize input when using in filesystem operations.
Cross-platform: Works consistently across operating systems.

Source

PHP dirname Documentation

This tutorial covered the PHP dirname 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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