我试图验证一个简单的HTML5页面,它成功验证除了三个<？php包含被标记为错误的语句的实例之外的所有内容.我无法弄清楚是什么让它不带PHP标签.为什么会这样？以下是它输出的三个错误：Validation Output: 3 ErrorsLine 29, Column 5: Saw <?. Probable cause: Attempt to use an XML processing instruction in HTML. (XML processing instructions are not supported in HTML.)<?php include("inc/main-menu.php"); ?>Line 87, Colu...