How can PHP developers ensure the security of scripts that involve file handling and storage?

PHP developers can ensure the security of scripts that involve file handling and storage by implementing proper input validation, using secure file permissions, and avoiding direct user input in file paths. It is also important to sanitize user input to prevent against directory traversal attacks. 

// Example of input validation and secure file handling in PHP
$filename = $_POST['filename']; // Assume this is user input
$directory = '/path/to/upload/directory/';

// Validate filename
if (preg_match('/^[a-zA-Z0-9_-]+\.txt$/', $filename)) {
    // Sanitize user input
    $safe_filename = basename($filename);
    
    // Set secure file path
    $filepath = $directory . $safe_filename;

    // Check if file already exists
    if (!file_exists($filepath)) {
        // Proceed with file handling operations
        // e.g. file_put_contents($filepath, 'File content');
    } else {
        echo 'File already exists.';
    }
} else {
    echo 'Invalid filename format.';
}

Keywords

PHP file handling security storage functions

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