Provides a simple PHP mailer wrapper for contact foms.

PHPMailer Wrapper for Contact Forms.php

<?php
    /**
     * Ensure you define the following constants - for example:
     *
     * define('SMTP_FROM', 'noreply@example.com');
     * define('MAIL_TO',   'rcpt@example.com');
     *
     * // If using SMTP transport:
     * define('SMTP_HOST', 'smtp.example.com');
     * define('SMTP_PORT', '25'); // 25, 465, 587, 2525 are common options
     * define('SMTP_USER', 'sender@example.com');  // defaults to ''
     * define('SMTP_PASS', 'SMTP_USER Password');  // defaults to ''
     */

    include __DIR__ . '/PHPMailer-6.9.1/src/Exception.php';
    include __DIR__ . '/PHPMailer-6.9.1/src/PHPMailer.php';
    include __DIR__ . '/PHPMailer-6.9.1/src/SMTP.php';

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

    /**
     * This is a helper function around PHP Mailer.
     * Server parameters are configured with the above declarations.
     * Email-specific functions are dictated within the 'data' array.
     *
     * @author Shane Thompson <me@shane.pt>
     *
     * @param array $args {
     *    An array of arguments.
     *
     *      @type array  $to        Required. Takes an array of address fields.
     *           $to = [
     *               'user1@example.com,
     *               ['user2@example.com', 'John Doe]
     *           ]
     *      @type array  $cc        Optional. Same format as $to.
     *      @type array  $bcc       Optional. Same format as $to.
     *      @type array  $reply-to  Optional. Same format as $to.
     *      @type string $subject   Required.
     *      @type string $body      Optional. If not specified, will be generated from supplied fields.
     *      @type string $transport Optional. 'smtp', 'sendmail' or 'mail'. If not specified, tests the
     *                                environment in that order.
     *      @type bool   $debug     Optional. Enables debugging. Defaults to false.
     *      @type string *          Optional. Any remaining contact form fields from which to generate
     *                                an email body.
     * } /args
     */
    function send_email(array $args) {
        $SMTP_FROM = 'noreply@' . $_SERVER['HTTP_HOST'];
        $SMTP_PORT = 25;
        $SMTP_USER = '';
        $SMTP_PASS = '';

        if (defined('SMTP_FROM')) $SMTP_FROM = SMTP_FROM;
        if (defined('SMTP_PORT')) $SMTP_PORT = SMTP_PORT;
        if (defined('SMTP_USER')) $SMTP_USER = SMTP_USER;
        if (defined('SMTP_PASS')) $SMTP_PASS = SMTP_PASS;

        if (!array_key_exists('to', $args) ||
            !array_key_exists('subject', $args))
        {
            throw new ValueError(sprintf(
                '%s missing required keys.', __FUNC__
            ));
        }

        $allowed_transports = array('smtp', 'sendmail', 'mail');
        if (! array_key_exists('transport', $args) ||
            ! in_array($args['transport'], $allowed_transports))
        {
            if (defined('SMTP_HOST')) {
                $args['transport'] = 'smtp';
            } elseif (ini_get('sendmail_path')) {
                $args['transport'] = 'sendmail';
            } elseif (function_exists('mail')) {
                $args['transport'] = 'mail';
            } else {
                throw new \RuntimeException(
                    'No valid mail transport could be detected. ' .
                    'Please configure a valid mail transport.'
                );
            }
        }

        if (! array_key_exists('debug', $args)) {
            $args['debug'] = false;
        }

        $mail = new PHPMailer;

        if ($args['debug']) {
            $mail->Debugoutput = $args['debug'];
            $mail->SMTPDebug = 2;
        }

        call_user_func([$mail, 'is' . $args['transport']]);

        if ('smtp' === $args['transport']) {
            if (! defined('SMTP_HOST')) {
                throw new RuntimeException(sprintf(
                    '%s: No SMTP_HOST defined.', __FUNC__
                ));
            }

            $mail->Host = SMTP_HOST;

            if (!empty($SMTP_USER) && !empty($SMTP_PASS)) {
                $mail->SMTPAuth   = true;
                $mail->Username   = $SMTP_USER;
                $mail->Password   = $SMTP_PASS;
            }

            $mail->port = $SMTP_PORT;
            switch ($mail->port) {
                case 465:
                    $mail->SMTPSecure = PHPMailer::ENCRYPTION_SMTPS;
                    break;
                case 587:
                    $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
                    break;
                case 25:
                default:
                    $mail->SMTPSecure = '';     // No encryption
                    $mail->SMTPAutoTLS = true;  // Automatically negotiate TLS connections where supported
                    break;
            }
        }

        //Recipients
        $mail->setFrom($SMTP_FROM);

        // Add all addresses
        foreach (['to', 'cc', 'bcc', 'reply-to'] as $func) {
            if (! array_key_exists($func, $args)) {
                continue;
            }

            foreach ($args[$func] as $rcpt) {
                if (!is_array($rcpt)) {
                    $rcpt = [$rcpt, ''];
                }

                if ('reply-to' === $func) {
                    $func = 'ReplyTo';
                }

                if ('addto' === ($method = "add{$func}")) {
                    $method = 'addAddress';
                }

                call_user_func_array(array($mail, $method), $rcpt);
            }
        }

        $body = '';

        // Generate a generic body output to fall back upon
        $skip_keys = array('subject', 'body', 'to', 'cc', 'bcc', 'reply-to', 'transport', 'debug');
        foreach ($args as $key=>$val) {
            if (in_array($key, $skip_keys, true)) {
                continue;
            }

            $body .= sprintf(
                '<b>%s</b> %s<br/>',
                htmlspecialchars($key),
                nl2br(htmlspecialchars($val))
            );
        }

        //Content
        $mail->isHTML(true);                                  //Set email format to HTML
        $mail->Subject = $args['subject'];
        $mail->Body    = $args['body'] ?: $body;
        $mail->AltBody = strip_tags(preg_replace('/\<br(\s*)?\/?\>/i', "\n", $mail->Body));

        return $mail->send();
    }