mail.php

<?php
// Settings
  $name        = "Aditya";
  $email       = "adityasuman2025@gmail.com";
  
  $to          = "$name <$email>";
  $subject     = "Here is your attachment";
  
  $mainMessage = "Hi, here's the file.";

  $website = $_SERVER['HTTP_HOST'];
  $quotation_num = 22;
  $fileatt     = "http://" . $website . "/invoice/Invoice-" . $quotation_num . ".pdf"; //file location
  $fileatttype = "application/pdf";
  $fileattname = "Invoice-" . $quotation_num . ".pdf"; //name that you want to use to send or you can use the same name
  
  $headers = "From: voltatech@pnds.in";

  // File
  $file = fopen($fileatt, 'rb');
  $data = fread($file, 10000);
  fclose($file);

  // This attaches the file
  $semi_rand     = md5(time());
  $mime_boundary = "==Multipart_Boundary_x{$semi_rand}x";
  $headers      .= "\nMIME-Version: 1.0\n" .
    "Content-Type: multipart/mixed;\n" .
    " boundary=\"{$mime_boundary}\"";
    $message = "This is a multi-part message in MIME format.\n\n" .
    "--{$mime_boundary}\n" .
    "Content-Type: text/plain; charset=\"iso-8859-1\n" .
    "Content-Transfer-Encoding: 7bit\n\n" .
    $mainMessage  . "\n\n";

  $data = chunk_split(base64_encode($data));
  $message .= "--{$mime_boundary}\n" .
    "Content-Type: {$fileatttype};\n" .
    " name=\"{$fileattname}\"\n" .
    "Content-Disposition: attachment;\n" .
    " filename=\"{$fileattname}\"\n" .
    "Content-Transfer-Encoding: base64\n\n" .
  $data . "\n\n" .
   "--{$mime_boundary}--\n";

  // Send the email
  if(mail($to, $subject, $message, $headers)) {

    echo "The email was sent.";

  }
  else {

    echo "There was an error sending the mail.";
  }

?>