PHP study notes: form processing and data validation

PHP Study Notes: Form Processing and Data Validation

In web development, forms are one of the important components for users to interact with the website. When users fill out forms and submit data on the website, the website needs to process and verify the submitted data to ensure the accuracy and security of the data. This article will introduce how to use PHP to process forms and perform data validation, and provide specific code examples.

1. Form submission and data preprocessing
   In HTML, we need to use the
   tag to create a form and specify the form's submission method and target address. Generally speaking, the form submission method can be GET or POST. In PHP, the data submitted by the form can be obtained through the $_GET and $_POST superglobal variables.

Code example:

<form action="form.php" method="post">
    <input type="text" name="username" placeholder="请输入用户名">
    <input type="password" name="password" placeholder="请输入密码">
    <input type="submit" value="提交">
</form>

In the above code, we create a form containing username and password input boxes, and set the form's submission method to POST, and the target address is "form.php". When the user clicks the submit button, the form data will be submitted to "form.php" for processing. In "form.php", we can use $_POST['username'] and $_POST['password'] to get the values ​​of username and password.

2. Data Verification
   In order to ensure the accuracy and security of the data, we need to verify the data submitted by the user. Here are some common data validation methods:

• Non-null validation: Check whether the user has filled in the required fields.

if (empty($_POST['username'])) {
    echo "用户名不能为空";
}

• Length limit: Limit the length of username and password.

if (strlen($_POST['username']) < 6 || strlen($_POST['username']) > 20) {
    echo "用户名长度必须在6-20个字符之间";
}

• Data format verification: Check whether user input conforms to a specific format, such as email, mobile phone number, etc.

if (!filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
    echo "请输入有效的邮箱地址";
}

• Data filtering: Filter special characters in user input to prevent security issues such as SQL injection.

$username = mysqli_real_escape_string($conn, $_POST['username']);
$password = mysqli_real_escape_string($conn, $_POST['password']);

In the above example, we used PHP's built-in filter_var function to perform data format verification, and used the mysqli_real_escape_string function to filter user input.

3. Complete form processing example
   The following is a complete form processing example, including form submission and data validation:

<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    // 数据预处理
    $username = $_POST['username'];
    $password = $_POST['password'];

    // 数据验证
    if (empty($username) || empty($password)) {
        echo "用户名和密码不能为空";
    } elseif (strlen($username) < 6 || strlen($username) > 20) {
        echo "用户名长度必须在6-20个字符之间";
    } else {
        // 数据插入或其他业务处理
        // ...
        echo "表单提交成功";
    }
}
?>
<form action="" method="post">
    <input type="text" name="username" placeholder="请输入用户名">
    <input type="password" name="password" placeholder="请输入密码">
    <input type="submit" value="提交">
</form>

In the above example, we Determine whether the form is submitted by judging whether $_SERVER['REQUEST_METHOD'] is equal to 'POST'. Then, we perform data preprocessing and verification, and execute corresponding logic based on the verification results. If the verification passes, we can insert the data into the database or perform other business processing.

Summary
Through the study of this article, we have learned how to use PHP to process forms and perform data validation. Form processing and data validation are a very important part of website development, which can ensure the accuracy and security of data submitted by users. I hope the content of this article can be helpful to PHP beginners.

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