How can PHP developers ensure cross-client compatibility when sending HTML emails with embedded images?

To ensure cross-client compatibility when sending HTML emails with embedded images, PHP developers should use absolute URLs for the image sources and include a plain text alternative in the email body. This helps ensure that the images are displayed correctly across different email clients and devices. 

$to = 'recipient@example.com';
$subject = 'HTML Email with Embedded Image';
$boundary = md5(uniqid(time()));

$headers = "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: multipart/related; boundary=\"{$boundary}\"\r\n";

$message = "--{$boundary}\r\n";
$message .= "Content-Type: text/html; charset=\"UTF-8\"\r\n";
$message .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
$message .= "<html><body>";
$message .= "<img src=\"https://example.com/image.jpg\" alt=\"Embedded Image\">";
$message .= "</body></html>\r\n";

$message .= "--{$boundary}\r\n";
$message .= "Content-Type: image/jpeg\r\n";
$message .= "Content-Transfer-Encoding: base64\r\n";
$message .= "Content-ID: <image.jpg>\r\n\r\n";
$message .= base64_encode(file_get_contents('image.jpg')) . "\r\n";

$message .= "--{$boundary}--";

mail($to, $subject, $message, $headers);

Keywords

PHP HTML emails embedded images cross-client compatibility MIME types

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