很多时候，我可能会检查post数据中是否存在变量，然后做一些事情。我很难理解用户创建或更新帖子时发生了什么。我做任何类型的后端功能都没有问题，但是当我想输出一些东西时，我猜页面被重新定向了？您通常如何处理这项常见任务？如何基于post变量的存在或任何即时操作创建管理通知？

这里发生了什么：

<?php
/*
 Plugin Name: Echo something on presence of variable
 Plugin URI: http://wordpress-bdd.com/
 Description: Hooking into the redirect with post variables
 */

class WhatIsGoingOn{

    public function __construct(){
        //add meta box:
        add_action(\'load-post.php\', array($this, \'doAddMetaBoxes\'));
        add_action(\'load-post-new.php\', array($this, \'doAddMetaBoxes\'));
        $this->whyCantIechoThisNotice();
     }

    public function doAddMetaBoxes(){
        add_meta_box(\'metaWithInput\', \'Hello\', array($this, \'echoMetaBox\'), \'post\', \'side\', \'high\');
    }

    public function echoMetaBox(){
        echo("<input type = \'text\' name = \'myInput\' id = \'myInput\' />");
    }

     public function whyCantIechoThisNotice(){

        //check for presence of variable and do something:
        if (isset($_POST[\'myInput\']) && (!($_POST[\'myInput\'] == ""))){
            //If this line is uncomented, the die fires
            //die(\'I am here!\');
            //How do I get the notice to echo?
                echo ("
                        <div class=\'notice notice-success is-dismissible\'>
                                <p>This is a notice</p>
                        </div>
                ");
        }
    }

}

$WhatIsGoingOn = new WhatIsGoingOn;