mailTemplate - Send an email using a PHP template file.

mailTemplate($_filename, $_v) causes the PHP engine to parse the PHP file specified by $_filename, with the variables passed in the variable $_v, which should output an RFC-822 (and its successors) style message. The function then extracts the headers from the message, grabs the "To" and "Subject" lines from it, and then passes the "To:", "Subject:", message body, and remaining headers, to the PHP mail() function.

As an example, consider template file "thanks.php"

To: <<?= $email ?>>
Subject: Thank you for your request
Content-Type: text/plain; charset=utf-8

Dear <?= $name =>,

Thankyou for your request, one of our staff will contact you <?= $when =>.
<?php if ($important) { ?>

Your request is important to us.
<?php } ?>

Which could then be called with:

mailTemplate("thanks.php", [
    'email' => "dave@example.com",
    'name' => "Dave",
    'when' => "tomorrow",
    'important' => FALSE,
]};

Note that, as of this implementation, $_filename is read using include(), so it uses the file-finding rules defined therein.

Also, it is worth remembering that PHP eats newlines directly following a PHP close tag. Therefore, if you have:

To: <?= $recipient ?>
Subject: ...

Then the newline following the close tag will be eaten by the PHP parser, and you'll end up with:

To: example@example.comSubject: ...

To work around this, you need to either make the closing tag not the last thing on the line (e.g. by adding a trailing space to the line), or forcibly output a newline yourself from within the PHP, e.g.:

To: <?= $recipient."\n" ?>
Subject: ...