必填字段将以正确的方式检查字段是否填充.大多数情况下，我们将 * 符号用于必填字段.
验证意味着检查用户提交的输入. PHP中有两种类型的验证.它们如下:<
客户端验证 : 验证在客户端计算机Web浏览器上执行.
服务器端验证 : 在数据提交后，数据已发送到服务器并在服务器计算机中执行验证检查.
| 字段 | 验证规则 |
|---|---|
| 名称 | 需要字母和空格 |
| 电子邮件 | 需要 @ 和. |
| 网站 | 需要有效的网址 |
| 收音机 | 必须至少选择一次 |
| 复选框 | 必须至少检查一次 |
| 下拉菜单 | 必须至少选择一次 |
以下代码显示网址验证
$website = input($_POST["site"]);
if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) {
$websiteErr = "Invalid URL";
}上述语法将验证给定的URL是否有效.它应该允许一些关键字为https，ftp，www，az，0-9，..等..
下面的代码显示验证电子邮件地址
$email = input($_POST["email"]);
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$emailErr = "Invalid format and please re-enter valid email";
}上面的语法将验证给定的电子邮件地址是否格式正确.如果不是，则会显示错误消息.
下面的示例显示了包含必填字段验证的表单
<html>
<head>
<style>
.error {color: #FF0000;}
</style>
</head>
<body>
<?php
// define variables and set to empty values
$nameErr = $emailErr = $genderErr = $websiteErr = "";
$name = $email = $gender = $comment = $website = "";
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if (empty($_POST["name"])) {
$nameErr = "Name is required";
}else {
$name = test_input($_POST["name"]);
}
if (empty($_POST["email"])) {
$emailErr = "Email is required";
}else {
$email = test_input($_POST["email"]);
// check if e-mail address is well-formed
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$emailErr = "Invalid email format";
}
}
if (empty($_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 = "Gender is required";
}else {
$gender = test_input($_POST["gender"]);
}
}
function test_input($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>
<h2>Absolute classes registration</h2>
<p><span class = "error">* required field.</span></p>
<form method = "post" action = "<?php
echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
<table>
<tr>
<td>Name:</td>
<td><input type = "text" name = "name">
<span class = "error">* <?php echo $nameErr;?></span>
</td>
</tr>
<tr>
<td>E-mail: </td>
<td><input type = "text" name = "email">
<span class = "error">* <?php echo $emailErr;?></span>
</td>
</tr>
<tr>
<td>Time:</td>
<td> <input type = "text" name = "website">
<span class = "error"><?php echo $websiteErr;?></span>
</td>
</tr>
<tr>
<td>Classes:</td>
<td> <textarea name = "comment" rows = "5" cols = "40"></textarea></td>
</tr>
<tr>
<td>Gender:</td>
<td>
<input type = "radio" name = "gender" value = "female">Female
<input type = "radio" name = "gender" value = "male">Male
<span class = "error">* <?php echo $genderErr;?></span>
</td>
</tr>
<td>
<input type = "submit" name = "submit" value = "Submit">
</td>
</table>
</form>
<?php
echo "<h2>Your given values are as:</h2>";
echo $name;
echo "<br>";
echo $email;
echo "<br>";
echo $website;
echo "<br>";
echo $comment;
echo "<br>";
echo $gender;
?>
</body>
</html>它将产生以下结果 :
