当表单中出现错误时，使文本框颜色为红色 [英] Making textbox color red when error occurs in a form

问题描述

我需要你的帮助..我想让文本框的红色，当一个窗体中有错误...

这是我能做到。但是当我提交fore，我得到一个未定义的索引 error_css 在形式

  if （$ _POST ['submit']））{
 if（empty（$ _ POST ['username']））{
 $ error_css ='background-color：red' 
} 
  

表单

 < label for =username>用户名：< / label> 
< input id =usernametype =textvalue =<？php if（isset（$ _ POST ['username']））{echo $ _POST ['username'];}？ ; name =usernametitle ='Username'/>感谢您的时间... 
 
 
 
 $ b >解决方案
尝试这样：
 <？php 
 
 $ username =; 
 $ error_css =; 
 
 if（isset（$ _ POST ['submit']））{
 if（isset（$ _ POST ['username']））
 $ username = $ _POST ['用户名']; 
 else 
 $ error_css ='background-color：red'; 
} 
 
？> 
 
< label for =username>用户名：< / label> 
< input id =usernametype =textvalue =<？php echo $ username;？> name =usernametitle ='Username'style =<？php echo $ error_css;？>/> 
  
 
I need your help.. I'm trying to make the textbox red whenever there's an error in a form...

This is what i've being able to do. But when i submit the fore, I get an Undefined Index error_css in the form
 if (isset($_POST['submit'])) { 
 if (empty($_POST['username'])) {
       $error_css='background-color:red';
 }
Form
<label for="username">Username:</label>
<input id="username" type="text" value="<?php if(isset($_POST['username'])){ echo $_POST['username']; } ?>" name="username" title='Username' />
thanks for your time...
解决方案
Try something like this:
<?php

$username = "";
$error_css = "";

if (isset($_POST['submit'])) {
    if(isset($_POST['username']))
        $username = $_POST['username'];
    else
        $error_css='background-color:red';
}

?>

<label for="username">Username:</label>
<input id="username" type="text" value="<?php echo $username; ?>" name="username" title='Username' style="<?php echo $error_css; ?>"/>


                        
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