PHPのmb_send_mail関数でファイルを添付してメールを送信するスクリプト

$to   = "mailto@example.jp";
$from = "mailfrom@example.jp";

$subject  = "件名";

$mailbody = "メール本文\n";

$boundary = md5(uniqid(rand())); //バウンダリー文字（パートの境界）


$header = "From: $to\n"
        . "Reply-To: $from\n"
        . "X-Mailer: PHP/".phpversion()."\n"
        . "MIME-version: 1.0\n"
        . "Content-Type: multipart/mixed;\n"
        . "\tboundary=\"$boundary\"\n";

$msg = "This is a multi-part message in MIME format.\n\n"
     . "--$boundary\n"
     . "Content-Type: text/plain; charset=iso-2022-jp\n"
     . "Content-Transfer-Encoding: 7bit\n\n"

     . $mailbody."\n"

     . "\n";


// 画像（upfileという名前でアップロードされたとする）
if($_FILES["upfile"]["error"] == UPLOAD_ERR_OK) {

    $tmp   = $_FILES["upfile"]["tmp_name"];
    $name  = $_FILES["upfile"]["name"];
    $size  = $_FILES["upfile"]["size"];

    $array = explode(".", $name);
    $nr    = @count($array);
    $ext   = $array[$nr - 1];

    $name  = date("U").".".$ext;

    $fp = fopen($tmp, "r");
    $contents = fread($fp, filesize($tmp));
    fclose($fp);
    $f_encoded = chunk_split(base64_encode($contents)); //エンコード

    $msg .= "--$boundary\n"
         . "Content-Type: application/octet-stream;\n"
         . "\tname=\"$name\"\n"
         . "Content-Transfer-Encoding: base64\n"
         . "Content-Disposition: attachment;\n"
         . "\tfilename=\"$name\"\n\n"
         . "$f_encoded\n"
         . "\n";

} //[end if]


// language establish
mb_language("ja");

// original encoding
$orgEncoding = mb_internal_encoding();

// specify internal encoding
mb_internal_encoding("utf-8") ;


//メール送信
if(!mb_send_mail($mailto, $subject, $msg, $header)) {
    echo "メールの送信に失敗しました。";
}

// internal encoding take back
mb_internal_encoding($orgEncoding);