PHP unlink Function

last modified April 3, 2025

The PHP unlink function deletes a file from the filesystem. It’s essential for file management operations in PHP applications.

Basic Definition

The unlink function removes a file specified by its path. It returns true on success or false on failure. The function is binary-safe.

Syntax: unlink(string $filename, resource $context = null): bool. The optional context parameter can be used with stream wrappers.

Basic unlink Example

This shows the simplest usage of unlink to delete a file.

basic_unlink.php

<?php

declare(strict_types=1);

$file = “test.txt”;

if (file_exists($file)) { if (unlink($file)) { echo “File deleted successfully”; } else { echo “Error deleting file”; } } else { echo “File does not exist”; }

This checks if the file exists before attempting deletion. The unlink function returns true if successful. Always verify file existence first.

Error Handling with unlink

Proper error handling is crucial when working with filesystem operations.

error_handling.php

<?php

declare(strict_types=1);

$file = “nonexistent.txt”;

try { if (!unlink($file)) { throw new RuntimeException(“Could not delete $file”); } echo “File deleted successfully”; } catch (RuntimeException $e) { error_log($e->getMessage()); echo “Error: " . $e->getMessage(); }

This demonstrates exception handling for file deletion. The code attempts to delete a file and throws an exception if unsuccessful. Errors are logged.

Deleting Files with Relative Paths

unlink works with both absolute and relative file paths.

relative_path.php

<?php

declare(strict_types=1);

$file = “../temp/old_data.csv”;

if (is_writable($file)) { if (unlink($file)) { echo “Temporary file removed”; } else { echo “Failed to remove temporary file”; } } else { echo “File not writable or doesn’t exist”; }

This checks file permissions before deletion using is_writable. Relative paths are resolved relative to the current working directory.

Using Context with unlink

The context parameter allows additional options for stream operations.

context_usage.php

<?php

declare(strict_types=1);

$file = “ftp://user:pass@example.com/tmp/file.txt"; $options = [‘ftp’ => [‘overwrite’ => true]]; $context = stream_context_create($options);

if (unlink($file, $context)) { echo “Remote file deleted successfully”; } else { echo “Failed to delete remote file”; }

This shows how to delete a file via FTP using a stream context. The context provides authentication and additional FTP-specific options.

Secure File Deletion

Security considerations are important when deleting files in PHP.

secure_deletion.php

<?php

declare(strict_types=1);

function secureDelete(string $path): bool { if (!file_exists($path)) { return false; }

if (!is_file($path)) {
    return false;
}

$realpath = realpath($path);
$allowedDir = realpath(__DIR__ . '/uploads');

if (strpos($realpath, $allowedDir) !== 0) {
    return false;
}

return unlink($realpath);

}

$file = “uploads/user_upload.jpg”; if (secureDelete($file)) { echo “File securely deleted”; } else { echo “Deletion failed or not allowed”; }

This secure deletion function validates the file path thoroughly. It checks if the file exists, is a regular file, and is within an allowed directory.

Best Practices

• Check Permissions: Verify file is writable before deletion.

• Error Handling: Implement proper error handling mechanisms.

• Path Validation: Validate paths to prevent directory traversal.

• Backup: Consider backup before critical deletions.

• Logging: Log deletion operations for audit purposes.

Source

PHP unlink Documentation

This tutorial covered the PHP unlink function with practical examples showing file deletion in different scenarios with security in mind.

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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