Php为全局变量返回NULL

Question

So I have the following code:

public function pcieh_shortcodes_init() {
    $data = $this->data;
    var_dump($data); //Return an array which is Expected       

    function pcieh_shortcode($atts = [], $content = null) {
         global $data;
         var_dump($data); //Return NULL
     }

    add_shortcode('pcieh', 'pcieh_shortcode');
}

When I call pcieh_shortcodes_int I expect the $data inside pcieh_shortcode to have the same value as outside $data since it's global but it returns NULL. Why is that and how can I fix it?

Answer 1

Instead of this

 public function pcieh_shortcodes_init() {
     $data = $this->data;
     var_dump($data); //Return an array which is Expected       

     function pcieh_shortcode($atts = [], $content = null) {
          global $data;
          var_dump($data); //Return NULL
      }

     add_shortcode('pcieh', 'pcieh_shortcode');
 }

Why not this

public function pcieh_shortcodes_init() {
    $data = $this->data;
    var_dump($data); //Return an array which is Expected       
    add_shortcode('pcieh', [$this,'pcieh_shortcode']);
}

public function pcieh_shortcode($atts = [], $content = null) {
    var_dump($this->data); //Return NULL
}

Then there is no need for global or any of the ugliness associated with it. It's perfectly acceptable to pass a class and method in as an array.

Basically wordpress is using call_user_func to call this anyway.

http://php.net/manual/en/function.call-user-func.php

UPDATE

I should have noted, in the original code in the question, even if you did get it to work, you have no reference to the actual instance of this class, so any value you set in data (after assign the short code, and global) would have likely been lost anyway. In other words you would lose the state of the current object and any data it contains.

So by using the actual instance $this you can be sure you are actually dealing with the instance you want to.