Function to send html mail. It reads the body and converts images to base64 inline attachments. It appends a header and foother. You can also send additional inline attachments via $attachments and it has ical support.

mailprocessor.php

<?php

function sendmail($to, $from $subject, $body, $preheader=false, $attachments=false, $noDom=false, $dstName=false, $url){
        $obj = new stdClass();
        //Create a new PHPMailer instance
        $mail = new PHPMailer;
        $msg="";
        $mail->SMTPSecure = "tls";
        $mail->IsSMTP();
        $mail->Host = "smtp.gmail.com";
        $mail->Port = "587";
        $mail->SMTPAuth = true;
        $mail->Username = '';
        $mail->Password = '';
        $mail->AddReplyTo($from);
        $mail->setFrom($from, $from);
        //Set who the message is to be sent to
        if($dstName)
        $mail->addAddress($to, $dstName);
        else
        $mail->addAddress($to);
        if(empty($preheader))
        $preheader=$subject; 
        $msg="";
        $idx=0;
        if(trim($body)!="" && !$noDom ){
            $doc=new DOMDocument();
            @$doc->loadHTML($body);
            $xml=simplexml_import_dom($doc); // just to make xpath more simple
            $images=$xml->xpath('//img');
            foreach ($images as $img) {
                $sourceBase64=$img['src'];
                $dataFilename= $img['data-filename'];
                $fileName=pathinfo($img['data-filename'], PATHINFO_FILENAME); 
                $fileExtension=pathinfo($img['data-filename'], PATHINFO_EXTENSION);
                if(empty($fileName))
                $fileName=uniqid();
                if(empty($fileExtension))
                $fileExtension="png";
                if(preg_match("|data:image/png;base64,|", $sourceBase64)){
                    $mail->addStringEmbeddedImage(base64_decode(str_replace("data:image/png;base64,", "", $sourceBase64)), "${fileName}_{$idx}", "${fileName}_{$idx}.{$fileExtension}");
                    $body=str_replace("data:image/png;base64,".$sourceBase64, "cid:${fileName}_{$idx}", $body); 
                } else {
                    $mail->addStringEmbeddedImage(file_get_contents($sourceBase64), "${fileName}_{$idx}", "${fileName}_{$idx}.{$fileExtension}");
                    $body=str_replace($sourceBase64, "cid:${fileName}_{$idx}", $body); 
                }
            }
        }

        
        ob_start(); 
        include(dirname(__FILE__)."header.php");
        $header=ob_get_contents();
        ob_end_clean();
        ob_start(); 
        include(dirname(__FILE__)."email.footer.php");
        $footer=ob_get_contents();
        ob_end_clean();
        
        $msg=$header.$body.$footer;
        $mail->Subject = $subject;
        $mail->msgHTML($msg);
        if(is_array($attachments) && sizeof($attachments)>0)
        foreach($attachments as $attach){
            if($attach['name']=="ical")
            $mail->addStringAttachment($attach['src'],'ical.ics','base64','text/calendar');
            else
            $mail->addStringAttachment(base64_decode($attach['src']), $attach['name']);
        }
        if (!$mail->send()) {
            $obj->error = __("Message could not be sent")." ". $mail->ErrorInfo;
            $obj->code[]=$t['code'];
        } else {
            $obj->success = __("Message sent");
        }
        return $obj;
    }