PHP

Add a Custom Header to a Related Item

Demonstrates the Chilkat Email.AddRelatedHeader method, which adds a custom MIME header field to an existing related item identified by its zero-based index. This example first adds a related style sheet (which becomes index 0) and captures its generated Content-ID, builds an HTML body that references the style sheet by that cid:, then attaches an extra header field to the related item and prints the resulting MIME.

Background: Like attachments, each related item (an inline image, style sheet, etc.) is a MIME part with its own small header block describing that part — Content-Type, Content-ID, Content-Location, and so on. AddRelatedHeader lets you insert additional fields into that per-part block, which is occasionally required for interoperability with clients that look for specific custom headers on embedded resources.

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<?php

use Chilkat2\Email;
use Chilkat2\StringBuilder;

// Demonstrates the AddRelatedHeader method, which adds a custom MIME header field to an
// existing related item, identified by its zero-based index.

$email = new Email();
$email->Subject = 'Related item with a custom header';

// Add a related item first (a style sheet); capture its generated Content-ID.  It becomes
// related-item index 0.
try {
    $cid = $email->AddRelatedString('styles.css', 'body { color: black; }', 'utf-8');
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// Build the HTML body, referencing the related style sheet by its Content-ID.  A
// placeholder is used and then replaced with the actual Content-ID.
$sbHtml = new StringBuilder();
$sbHtml->Append('<html><head><link rel="stylesheet" href="cid:PLACEHOLDER_CID"/></head><body>Styled content.</body></html>');
$numReplaced = $sbHtml->Replace('PLACEHOLDER_CID', $cid);
$email->SetHtmlBody($sbHtml->GetAsString());

// Add a custom header field to the first related item (index 0).
$email->AddRelatedHeader(0, 'X-Custom-Related-Header', 'some value');

// The custom header now appears in the related item's MIME part.
echo $email->GetMime(), "\n";