wp-rest

gistfile1.txt

    /*
        honestly, i only use wp-rest now for ajax, so mine would actually look somehting like this:
    */
    
      add_action('rest_api_init',function($server){
        register_rest_route('my-plugin/v1','/add-email',array(
          'methods' =>  'POST',
          'callback' => array($this,'add_email') //and i use class-based name-spacing and auto-loading as you can see
        ) );
      });
      
        
        // then we do the work down here in the function (this generic method is fine because it's inside a class)
      
      public function add_email(){
      
        // in here we would get our post data by accessing $_POST vars
        
        // we would then call the acf function for update_field() i forget what it actually is
        
        $field = update_field($some_id,$_POST['field']);
        
        return $field; // at least true or false, probably an id value for true
        
      }