What are common pitfalls when sending emails with attachments in PHP, and how can they be avoided?

// Example of sending an email with attachment in PHP

$to = "recipient@example.com";
$subject = "Test email with attachment";
$message = "This is a test email with attachment.";

// Path to the attachment file
$attachment = "/path/to/attachment.pdf";

// Read the attachment file content
$file_content = file_get_contents($attachment);

// Encode the attachment data
$encoded_content = chunk_split(base64_encode($file_content));

// Set the MIME type for the attachment
$mime_type = mime_content_type($attachment);

// Create the email headers
$headers = "From: sender@example.com\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: multipart/mixed; boundary=\"boundary\"\r\n";

// Build the email content
$email_content = "--boundary\r\n";
$email_content .= "Content-Type: text/plain; charset=\"utf-8\"\r\n";
$email_content .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
$email_content .= $message . "\r\n\r\n";
$email_content .= "--boundary\r\n";
$email_content .= "Content-Type: " . $mime_type . "; name=\"" . basename($attachment) . "\"\r\n";
$email_content .= "Content-Transfer-Encoding: base64\r\n";
$email_content .= "Content-Disposition: attachment; filename=\"" . basename($attachment) . "\"\r\n\r\n";
$email_content .= $encoded_content . "\r\n";
$email_content .= "--boundary--";

// Send the email with attachment
mail($to, $subject, $email_content, $headers);