update

demo/mask_detection/web/index.php

 <?php
-$json_string = file_get_contents("./video/result/2-mask_detection.json"); 
+$json_string = file_get_contents(".\\video\\result\\2-mask_detection.json"); 
 // 用参数true把JSON字符串强制转成PHP数组 
 $data_o = json_decode($json_string, true);
 ?>