How can developers ensure the reliability and efficiency of email attachment functionality in PHP scripts?

// Example PHP code snippet to ensure reliability and efficiency of email attachment functionality

// Validate and sanitize user input for file attachment
if(isset($_FILES['attachment']) && $_FILES['attachment']['error'] == UPLOAD_ERR_OK) {
    $attachment_name = $_FILES['attachment']['name'];
    $attachment_tmp_name = $_FILES['attachment']['tmp_name'];
    $attachment_size = $_FILES['attachment']['size'];
}

// Handle file upload securely
$upload_dir = 'attachments/';
$attachment_path = $upload_dir . $attachment_name;

if(move_uploaded_file($attachment_tmp_name, $attachment_path)) {
    // File successfully uploaded, continue with email sending process
} else {
    // Error handling for file upload failure
    echo "Error uploading file.";
}

// Implement error handling for any issues that may arise during attachment process
try {
    // Code to send email with attachment
} catch (Exception $e) {
    // Error handling for email sending failure
    echo "Error sending email with attachment: " . $e->getMessage();
}