在PHP網(wǎng)站開發(fā)建設(shè)中，用戶注冊(cè)、登錄，留言等等是必不可少的一些實(shí)用功能，用戶提交的信息數(shù)據(jù)都是通過form表單提交，然而提交的數(shù)據(jù)難免會(huì)有這樣或者那樣的錯(cuò)誤，不管是有心還是無意，為了保證數(shù)據(jù)的完整性、安全性，PHP form表單驗(yàn)證是過濾數(shù)據(jù)的必不可少的環(huán)節(jié)。
首先我們對(duì)用戶所有提交的數(shù)據(jù)都通過 PHP 的 htmlspecialchars() 函數(shù)處理。把特殊字符轉(zhuǎn)換為 HTML 實(shí)體。這意味著 < 和 > 之類的 HTML 字符會(huì)被替換為 < 和 > 。這樣可防止攻擊者通過在表單中注入 HTML 或 JavaScript 代碼（跨站點(diǎn)腳本攻擊）對(duì)代碼進(jìn)行利用。
當(dāng)用戶提交表單時(shí)，我們將做以下兩件事情，：
使用 PHP trim() 函數(shù)去除用戶輸入數(shù)據(jù)中不必要的字符 (如：空格，tab，換行)。
使用PHP stripslashes()函數(shù)去除用戶輸入數(shù)據(jù)中的反斜杠 (\)
必須字段
| 字段 | 驗(yàn)證規(guī)則 |
| Name | 必需。必須包含字母和空格。 |
| 必需。必須包含有效的電子郵件地址（包含 @ 和 .）。 | |
| Website | 可選。如果選填，則必須包含有效的 URL。 |
| Comment | 可選。多行輸入字段（文本框）。 |
上述字段是必須的，不能為空。
格式匹配
1、匹配姓名
“/^[a-zA-Z ]*$/”?
只允許空格和字母，”^”表示開頭，”$”表示結(jié)尾，[a-zA-Z ]表示a-z或者A-Z或者空格中的一個(gè)字符。
其實(shí)例代碼如下：
<?php
$name = test_input($_POST["name"]);
if (!preg_match("/^[a-zA-Z ]*$/",$name)) {
$nameErr = "只允許字母和空格！";
}
?>2、匹配E-mail
“/([\w-]+\@[\w-]+.[\w-]+)/”
“\w”匹配包括下劃線的任何單詞字符。等價(jià)于’[A-Za-z0-9_]’；
+匹配前面的子表達(dá)式一次或多次；
“-“匹配”-“。
3、匹配URL
“/\b(?:(?:https?|ftp):\/\/|www.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i”
保留表單中的值
在用戶點(diǎn)擊提交按鈕后，為確保字段值是否輸入正確，我們?cè)贖TML的input元素中插添加PHP腳本， 各字段名為: name, email, 和 website。 在評(píng)論的 textarea 字段中，我們將腳本放于 標(biāo)簽之間。 PHP腳本輸出值為： $name, $email, $website, 和 $comment 變量。
例如如下的代碼：
Name: <input type="text" name="name" value="<?php echo $name;?>"> E-mail: <input type="text" name="email" value="<?php echo $email;?>"> Website: <input type="text" name="website" value="<?php echo $website;?>"> Comment: <textarea name="comment" rows="5" cols="40"><?php echo $comment;?></textarea>
來一個(gè)PHP表單驗(yàn)證完整實(shí)例,其代碼如下：
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>form</title>
<style>
.error {color: #FF0000;}
</style>
</head>
<body>
<?php
// 定義變量并默認(rèn)設(shè)置為空值
$nameErr = $emailErr = $genderErr = $websiteErr = "";
$name = $email = $gender = $comment = $website = "";
if ($_SERVER["REQUEST_METHOD"] == "POST")
{
if (empty($_POST["name"]))
{
$nameErr = "名字是必需的";
}
else
{
$name = test_input($_POST["name"]);
// 檢測(cè)名字是否只包含字母跟空格
if (!preg_match("/^[a-zA-Z ]*$/",$name))
{
$nameErr = "只允許字母和空格";
}
}
if (empty($_POST["email"]))
{
$emailErr = "郵箱是必需的";
}
else
{
$email = test_input($_POST["email"]);
// 檢測(cè)郵箱是否合法
if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/",$email))
{
$emailErr = "非法郵箱格式";
}
}
if (empty($_POST["website"]))
{
$website = "";
}
else
{
$website = test_input($_POST["website"]);
// 檢測(cè) URL 地址是否合法
if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website))
{
$websiteErr = "非法的 URL 的地址";
}
}
if (empty($_POST["comment"]))
{
$comment = "";
}
else
{
$comment = test_input($_POST["comment"]);
}
if (empty($_POST["gender"]))
{
$genderErr = "性別是必需的";
}
else
{
$gender = test_input($_POST["gender"]);
}
}
function test_input($data)
{
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>
<h2>PHP 表單驗(yàn)證實(shí)例</h2>
<p><span class="error">* 必需字段。</span></p>
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
名字: <input type="text" name="name" value="<?php echo $name;?>">
<span class="error">* <?php echo $nameErr;?></span>
<br><br>
E-mail: <input type="text" name="email" value="<?php echo $email;?>">
<span class="error">* <?php echo $emailErr;?></span>
<br><br>
網(wǎng)址: <input type="text" name="website" value="<?php echo $website;?>">
<span class="error"><?php echo $websiteErr;?></span>
<br><br>
備注: <textarea name="comment" rows="5" cols="40"><?php echo $comment;?></textarea>
<br><br>
性別:
<input type="radio" name="gender" <?php if (isset($gender) && $gender=="female") echo "checked";?> value="female">女
<input type="radio" name="gender" <?php if (isset($gender) && $gender=="male") echo "checked";?> value="male">男
<span class="error">* <?php echo $genderErr;?></span>
<br><br>
<input type="submit" name="submit" value="Submit">
</form>
<?php
echo "<h2>您輸入的內(nèi)容是:</h2>";
echo $name;
echo "<br>";
echo $email;
echo "<br>";
echo $website;
echo "<br>";
echo $comment;
echo "<br>";
echo $gender;
?>
</body>
</html>以上這些將展示如何安全地處理 PHP 表單。對(duì) HTML 表單數(shù)據(jù)進(jìn)行適當(dāng)?shù)尿?yàn)證對(duì)于防范黑客和垃圾郵件很重要！
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