使用PHP / HTML突出显示表单验证中的空文本框

Question

I am trying to highlight the textboxes that are empty using ONLY php/html. Currently the background of the page changes color not the textbox. My question is how to define the PHP in the html tags

PHP:

if ($_SERVER["REQUEST_METHOD"] == "POST") {
            if (empty($_POST["fname"])) {
                $fname = "<div style='background-color:red'</div>";
            } else {
                $fname = test_input($_POST["fname"]);
            }

HTML:

<div class = "group">
                    <label for="name">First Name</label><br/>
                    <input type="text" id="fname" name="fname">
                    <span class="error">* <?php echo $fnameErr;?></span>

Answer 1

$fname = "background-color:red;'"; Try use <input type="text" id="fname" name="fname" style="<?php $fname;?>">