您可以使用apply_filters 功能：

function koku_crm_send_sendgrid($sendgrid_api_key, $to, $subject, $text, $html) {
  $to = apply_filters( \'koku_crm_send_to\', $to );

  $sendgrid = new \\SendGrid($sendgrid_api_key);
  $mail = new KCSendGrid\\Mail();
  $from = new KCSendGrid\\Email(get_bloginfo( \'name\' ), get_bloginfo( \'admin_email\' ));
  $mail->setFrom($from);
  $mail->setSubject(html_entity_decode($subject, ENT_QUOTES, \'UTF-8\'));

  $content = new KCSendGrid\\Content("text/plain", $text);
  $mail->addContent($content);

  $content = new KCSendGrid\\Content("text/html", $html);
  $mail->addContent($content);

  $personalization = new KCSendGrid\\Personalization();
  $to = new KCSendGrid\\Email(null, $to);
  $personalization->addTo($to);
  $mail->addPersonalization($personalization);

  $sendgrid->client->mail()->send()->post($mail);

}

的第一个参数apply_filters() 是筛选器的名称。这是你打电话时要用到的add_filter(). 第二个参数是要过滤的值。

现在您可以筛选$to 像这样：

function wpse_276933_send_to( $to ) {
  $to = \'[email protected]\';

  return $to;
}
add_filter( \'koku_crm_send_to\', \'wpse_276933_send_to\' );

通过将参数添加到，可以将更多值传递到过滤器回调函数中apply_filters(). 它们自己不会做任何事情，但这意味着它们在添加过滤器时可用。因此，如果您的过滤器是：

$to = apply_filters( \'koku_crm_send_to\', $to, $subject, $text );

您可以访问$subject 和$text 通过在回调函数中包含参数并设置add_filter() 到3, 使函数知道接受3个参数：

function wpse_276933_send_to( $to, $subject, $text ) {
  if ( $subject === \'Subject One\' ) {
    $to = \'[email protected]\';
  }

  return $to;
}
add_filter( \'koku_crm_send_to\', \'wpse_276933_send_to\', 10, 3 );

阅读插件手册中的更多内容：https://developer.wordpress.org/plugins/hooks/custom-hooks/