工作理念:

if (isset($_POST['submit'])) {
    $mailto = $_POST["mailTo"];
    $from_mail = $_POST["fromEmail"];
    $replyto = $_POST["fromEmail"];
    $from_name = $_POST["fromName"];
    $message = $_POST["message"];
    $subject = $_POST["subject"];

    $filename = $_FILES["fileAttach"]["name"];
    $content = chunk_split(base64_encode(file_get_contents($_FILES["fileAttach"]["tmp_name"])));

    $uid = md5(uniqid(time()));
    $name = basename($file);
    $header = "From: " . $from_name . " <" . $from_mail . ">\r\n";
    $header .= "Reply-To: " . $replyto . "\r\n";

    $header .= "MIME-Version: 1.0\r\n";
    $header .= "Content-Type: multipart/mixed; boundary=\"" . $uid . "\"\r\n\r\n";
    $header .= "This is a multi-part message in MIME format.\r\n";
    $header .= "--" . $uid . "\r\n";

// You add html "Content-type: text/html; charset=utf-8\n" or for Text "Content-type:text/plain; charset=iso-8859-1\r\n" by I.khan
    $header .= "Content-type:text/html; charset=utf-8\n";
    $header .= "Content-Transfer-Encoding: 7bit\r\n\r\n";

// User Message you can add HTML if You Selected HTML content
    $header .= "<div style='color: red'>" . $message . "</div>\r\n\r\n";

    $header .= "--" . $uid . "\r\n";
    $header .= "Content-Type: application/octet-stream; name=\"" . $filename . "\"\r\n"; // use different content types here
    $header .= "Content-Transfer-Encoding: base64\r\n";
    $header .= "Content-Disposition: attachment; filename=\"" . $filename . "\"\r\n\r\n"; // For Attachment
    $header .= $content . "\r\n\r\n";
    $header .= "--" . $uid . "--";
    if (mail($mailto, $subject, "", $header)) {
        echo "<script>alert('Success');</script>"; // or use booleans here
    } else {
        echo "<script>alert('Failed');</script>";
    }
}

从此页复制代码-在mail()中工作

他首先创建了一个可以稍后调用的mail_attachment函数。他稍后用他的附件代码来做。

<?php
function mail_attachment($filename, $path, $mailto, $from_mail, $from_name, $replyto, $subject, $message) {
    $file = $path.$filename;
    $file_size = filesize($file);
    $handle = fopen($file, "r");
    $content = fread($handle, $file_size);
    fclose($handle);
    $content = chunk_split(base64_encode($content));
    $uid = md5(uniqid(time()));
    $header = "From: ".$from_name." <".$from_mail.">\r\n";
    $header .= "Reply-To: ".$replyto."\r\n";
    $header .= "MIME-Version: 1.0\r\n";
    $header .= "Content-Type: multipart/mixed; boundary=\"".$uid."\"\r\n\r\n";
    $header .= "This is a multi-part message in MIME format.\r\n";
    $header .= "--".$uid."\r\n";
    $header .= "Content-type:text/plain; charset=iso-8859-1\r\n";
    $header .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
    $header .= $message."\r\n\r\n";
    $header .= "--".$uid."\r\n";
    $header .= "Content-Type: application/octet-stream; name=\"".$filename."\"\r\n"; // use different content types here
    $header .= "Content-Transfer-Encoding: base64\r\n";
    $header .= "Content-Disposition: attachment; filename=\"".$filename."\"\r\n\r\n";
    $header .= $content."\r\n\r\n";
    $header .= "--".$uid."--";
    if (mail($mailto, $subject, "", $header)) {
        echo "mail send ... OK"; // or use booleans here
    } else {
        echo "mail send ... ERROR!";
    }
}

//start editing and inputting attachment details here
$my_file = "somefile.zip";
$my_path = "/your_path/to_the_attachment/";
$my_name = "Olaf Lederer";
$my_mail = "my@mail.com";
$my_replyto = "my_reply_to@mail.net";
$my_subject = "This is a mail with attachment.";
$my_message = "Hallo,\r\ndo you like this script? I hope it will help.\r\n\r\ngr. Olaf";
mail_attachment($my_file, $my_path, "recipient@mail.org", $my_mail, $my_name, $my_replyto, $my_subject, $my_message);
?>

他在他的页面上有更多的细节，并在评论区回答了一些问题。

你可以使用我创建的这个类发送常规邮件或附件邮件。

下面是如何使用它的示例链接。

https://github.com/Nerdtrix/EZMAIL

要发送带有附件的电子邮件，我们需要使用multipart/mixed MIME类型，该类型指定混合类型将包含在电子邮件中。此外，我们希望使用多部分/替代MIME类型来发送纯文本和HTML版本的电子邮件。看一下这个例子:

<?php 
//define the receiver of the email 
$to = 'youraddress@example.com'; 
//define the subject of the email 
$subject = 'Test email with attachment'; 
//create a boundary string. It must be unique 
//so we use the MD5 algorithm to generate a random hash 
$random_hash = md5(date('r', time())); 
//define the headers we want passed. Note that they are separated with \r\n 
$headers = "From: webmaster@example.com\r\nReply-To: webmaster@example.com"; 
//add boundary string and mime type specification 
$headers .= "\r\nContent-Type: multipart/mixed; boundary=\"PHP-mixed-".$random_hash."\""; 
//read the atachment file contents into a string,
//encode it with MIME base64,
//and split it into smaller chunks
$attachment = chunk_split(base64_encode(file_get_contents('attachment.zip'))); 
//define the body of the message. 
ob_start(); //Turn on output buffering 
?> 
--PHP-mixed-<?php echo $random_hash; ?>  
Content-Type: multipart/alternative; boundary="PHP-alt-<?php echo $random_hash; ?>" 

--PHP-alt-<?php echo $random_hash; ?>  
Content-Type: text/plain; charset="iso-8859-1" 
Content-Transfer-Encoding: 7bit

Hello World!!! 
This is simple text email message. 

--PHP-alt-<?php echo $random_hash; ?>  
Content-Type: text/html; charset="iso-8859-1" 
Content-Transfer-Encoding: 7bit

<h2>Hello World!</h2> 
<p>This is something with <b>HTML</b> formatting.</p> 

--PHP-alt-<?php echo $random_hash; ?>-- 

--PHP-mixed-<?php echo $random_hash; ?>  
Content-Type: application/zip; name="attachment.zip"  
Content-Transfer-Encoding: base64  
Content-Disposition: attachment  

<?php echo $attachment; ?> 
--PHP-mixed-<?php echo $random_hash; ?>-- 

<?php 
//copy current buffer contents into $message variable and delete current output buffer 
$message = ob_get_clean(); 
//send the email 
$mail_sent = @mail( $to, $subject, $message, $headers ); 
//if the message is sent successfully print "Mail sent". Otherwise print "Mail failed" 
echo $mail_sent ? "Mail sent" : "Mail failed"; 
?>

正如你所看到的，发送带有附件的电子邮件很容易完成。在前面的例子中，我们有多部分/混合MIME类型，在里面我们有多部分/替代MIME类型，指定两个版本的电子邮件。为了将附件包含到消息中，我们将指定文件中的数据读入一个字符串，使用base64对其进行编码，将其分割为更小的块，以确保它与MIME规范匹配，然后将其作为附件包含。

从这里拍的。

我同意评论中的@MihaiIorga -使用PHPMailer脚本。听起来你拒绝是因为你想要更简单的选择。相信我，比起自己使用PHP内置的mail()函数，PHPMailer是一个更简单的选择。PHP的mail()函数真的不是很好。

使用PHPMailer:

下载PHPMailer脚本:http://github.com/PHPMailer/PHPMailer 提取归档文件并将脚本文件夹复制到项目中方便的位置。 包括主脚本文件——require_once('path/to/file/class.phpmailer.php');

现在，发送带有附件的电子邮件从异常困难变得异常简单:

use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

$email = new PHPMailer();
$email->SetFrom('you@example.com', 'Your Name'); //Name is optional
$email->Subject   = 'Message Subject';
$email->Body      = $bodytext;
$email->AddAddress( 'destinationaddress@example.com' );

$file_to_attach = 'PATH_OF_YOUR_FILE_HERE';

$email->AddAttachment( $file_to_attach , 'NameOfFile.pdf' );

return $email->Send();

只有一行$email-> addatattachment ();——再简单不过了。

如果使用PHP的mail()函数，则需要编写大量代码，并且可能会遇到许多很难找到的错误。

HTML代码:

<form enctype="multipart/form-data" method="POST" action=""> 
    <label>Your Name <input type="text" name="sender_name" /> </label> 
    <label>Your Email <input type="email" name="sender_email" /> </label> 
    <label>Your Contact Number <input type="tel" name="contactnumber" /> </label>
    <label>Subject <input type="text" name="subject" /> </label> 
    <label>Message <textarea name="description"></textarea> </label> 
    <label>Attachment <input type="file" name="attachment" /></label> 
    <label><input type="submit" name="button" value="Submit" /></label> 
</form> 

PHP代码:

<?php
if($_POST['button']){
{
    //Server Variables
    $server_name = "Your Name";
    $server_mail = "your_mail@domain.com";

    //Name Attributes of HTML FORM
    $sender_email = "sender_email";
    $sender_name = "sender_name";
    $contact = "contactnumber";
    $mail_subject = "subject";
    $input_file = "attachment";
    $message = "description";

    //Fetching HTML Values
    $sender_name = $_POST[$sender_name];
    $sender_mail = $_POST[$sender_email];
    $message = $_POST[$message];
    $contact= $_POST[$contact];
    $mail_subject = $_POST[$mail_subject];

    //Checking if File is uploaded
    if(isset($_FILES[$input_file])) 
    { 
        //Main Content
        $main_subject = "Subject seen on server's mail";
        $main_body = "Hello $server_name,<br><br> 
        $sender_name ,contacted you through your website and the details are as below: <br><br> 
        Name : $sender_name <br> 
        Contact Number : $contact <br> 
        Email : $sender_mail <br> 
        Subject : $mail_subject <br> 
        Message : $message.";

        //Reply Content
        $reply_subject = "Subject seen on sender's mail";
        $reply_body = "Hello $sender_name,<br> 
        \t Thank you for filling the contact form. We will revert back to you shortly.<br><br>
        This is an auto generated mail sent from our Mail Server.<br>
        Please do not reply to this mail.<br>
        Regards<br>
        $server_name";

//#############################DO NOT CHANGE ANYTHING BELOW THIS LINE#############################
        $filename= $_FILES[$input_file]['name'];
        $file = chunk_split(base64_encode(file_get_contents($_FILES[$input_file]['tmp_name'])));
        $uid = md5(uniqid(time()));
        //Sending mail to Server
        $retval = mail($server_mail, $main_subject, "--$uid\r\nContent-type:text/html; charset=iso-8859-1\r\nContent-Transfer-Encoding: 7bit\r\n\r\n $main_body \r\n\r\n--$uid\r\nContent-Type: application/octet-stream; name=\"$filename\"\r\nContent-Transfer-Encoding: base64\r\nContent-Disposition: attachment; filename=\"$filename\"\r\n\r\n$file\r\n\r\n--$uid--", "From: $sender_name <$sender_mail>\r\nReply-To: $sender_mail\r\nMIME-Version: 1.0\r\nContent-Type: multipart/mixed; boundary=\"$uid\"\r\n\r\n");
        //Sending mail to Sender
        $retval = mail($sender_mail, $reply_subject, $reply_body , "From: $server_name<$server_mail>\r\nMIME-Version: 1.0\r\nContent-type: text/html\r\n");
//#############################DO NOT CHANGE ANYTHING ABOVE THIS LINE#############################

        //Output
        if ($retval == true) {
            echo "Message sent successfully...";
            echo "<script>window.location.replace('index.html');</script>";
        } else {
            echo "Error<br>";
            echo "Message could not be sent...Try again later";
            echo "<script>window.location.replace('index.html');</script>";
        }
    }else{
        echo "Error<br>";
        echo "File Not Found";
    }
}else{
    echo "Error<br>";
    echo "Unauthorised Access";
}