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PHP Forms - Required field

This section will describe how to set the required form fields and error messages.

PHP - Required field

In the last chapter we have introduced the validation rules of the table, we can see the "Name", "E-mail", and "sex" field is required, each field can not be empty.

字段 验证规则
名字 必需。 + 只能包含字母和空格
E-mail 必需。 + 必需包含一个有效的电子邮件地址(包含"@"和".")
网址 可选。 如果存在,它必需包含一个有效的URL
备注 可选。多行字段(文本域)。
性别 必需。必需选择一个。

If in the previous chapter, all input fields are optional.

In the following code we added some new variables: $ nameErr, $ emailErr, $ genderErr, and $ websiteErr .. These errors will be displayed on the variables required fields. We have also added a if else statement for each $ _POST variable. These statements will check whether the $ _POST variable is empty (using php's empty () function). If empty, the corresponding error message is displayed. If not empty, the data will be passed to test_input () function:

// 定义变量并默认设为空值
$nameErr = $emailErr = $genderErr = $websiteErr = "";
$name = $email = $gender = $comment = $website = "";

  if (empty($_POST["name"])) {
    $nameErr = "名字是必需的。";
  } else {
    $name = test_input($_POST["name"]);

  if (empty($_POST["email"])) {
    $emailErr = "邮箱是必需的。";
  } else {
    $email = test_input($_POST["email"]);

  if (empty($_POST["website"])) {
    $website = "";
  } else {
    $website = test_input($_POST["website"]);

  if (empty($_POST["comment"])) {
    $comment = "";
  } else {
    $comment = test_input($_POST["comment"]);

  if (empty($_POST["gender"])) {
    $genderErr = "性别是必需的。";
  } else {
    $gender = test_input($_POST["gender"]);

PHP - error message

In the following examples of HTML form, we added some scripts for each field, each script will display an error message when the information input error. (If the user does not fill in the information and submit the form it will output an error message):

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>"> 
   名字: <input type="text" name="name">
   <span class="error">* <?php echo $nameErr;?></span>
   E-mail: <input type="text" name="email">
   <span class="error">* <?php echo $emailErr;?></span>
   网址: <input type="text" name="website">
   <span class="error"><?php echo $websiteErr;?></span>
   备注: <textarea name="comment" rows="5" cols="40"></textarea>
   <input type="radio" name="gender" value="female">女
   <input type="radio" name="gender" value="male">男
   <span class="error">* <?php echo $genderErr;?></span>
   <input type="submit" name="submit" value="Submit"> 

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