With the continuous development of the Internet, forms, as a basic interaction method, play a very important role in Web development. In PHP, handling form submission is an essential skill. This article will introduce how to handle form submission in PHP and give solutions to common form validation problems.

1. Basic process of form submission

Before processing form submission, let’s take a look at the basic process of form submission:

1. The user fills in the form in the browser form data and click the "Submit" button.

2. The browser encapsulates the form data into an HTTP request and sends it to the server.

3. The server receives the request and calls the corresponding PHP script for processing.

4. The PHP script processes the form data and returns the results to the browser.

5. The browser performs corresponding processing based on the returned results.

2. Methods for processing form submission in PHP

In PHP, there are many methods for processing form submission. The following two are commonly used:

1.POST method

When you submit a form using the POST method, the form data will be encapsulated in the message body of the HTTP request and will not be displayed in the URL. The POST method is usually used to submit forms involving passwords or other sensitive information, ensuring data security to a certain extent. In PHP, use the $_POST global variable to get the form data submitted by POST.

The following is a simple example:

if($_SERVER['REQUEST_METHOD'] == 'POST'){
    $username = $_POST['username'];
    $password = $_POST['password'];
}

2.GET method

When using the GET method to submit a form, the form data will be appended to the URL with "?" separated by "&". The GET method is often used to submit simple forms, such as search forms. In PHP, use the $_GET global variable to obtain GET submitted form data.

The following is a simple example:

if($_SERVER['REQUEST_METHOD'] == 'GET'){
    $keyword = $_GET['keyword'];
}

3. Form verification

Form submission not only needs to process the data submitted by the user, but also needs to verify the data to ensure that the data effectiveness and safety. Here are some common form validation problems and corresponding solutions.

1. Required field verification

Some fields in the form are required, such as user name, password, etc. If the user does not fill in these fields, a prompt message needs to be given to tell the user that these fields must be filled in. In PHP, you can use the isset() function to determine whether a variable exists. If the variable does not exist, it means the user did not fill in the corresponding field.

The following is a simple example:

if(isset($_POST['username']) && isset($_POST['password'])){
    //處理表單數(shù)據(jù)
}

2. Data format verification

Some fields in the form also need to be verified to be in correct format, such as email, mobile phone number, etc. In PHP, you can use regular expressions for validation. If the data format filled in by the user is incorrect, corresponding prompt information needs to be given.

The following is an example of verifying the email format:

$email = $_POST['email'];
if(!preg_match('/^w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*$/', $email)){
    //顯示錯(cuò)誤信息
    echo '郵箱格式不正確';
}

3. Prevent SQL injection

When processing user-submitted data, you need to pay attention to preventing SQL injection attacks. SQL injection is an attack method that exploits vulnerabilities in web applications to control the database or steal sensitive information by injecting SQL statements into forms.

In PHP, you can use the mysqli_real_escape_string() function to escape some special characters to avoid SQL injection attacks.

The following is an example:

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

//查詢數(shù)據(jù)庫
$sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";

4. Summary

Processing form submission is a very important skill in web development. In PHP, use the POST and GET methods to obtain form data, use the isset() function to verify required fields, use regular expressions to verify data format, and use the mysqli_real_escape_string() function to prevent SQL injection attacks. By studying this article, I believe that readers will be able to master the skills of processing form submission in PHP and be able to easily deal with common form validation problems.

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