Three ways to pass values ​​from PHP to HTML

PHP, as a back-end programming language, often interacts with front-end HTML. When writing this kind of interactive page, we need to use some methods to transfer variable values ​​​​in PHP to HTML to facilitate display and use on the front end. The following will introduce three ways of writing values ​​​​from PHP to HTML.

1. Use PHP's echo statement to output HTML code

Use PHP's echo statement to directly output HTML tags and variables in the PHP file. This is also the simplest and most basic method. You can directly call PHP variables in HTML, which is very flexible. For example, the following code can pass the value of the variable $message in PHP to the HTML page:

<?php
$message = "Hello World!";
echo "<p>" . $message . "</p>";
?>

In the HTML page, you only need to nest the paragraph generated by the above code to display the PHP message through the browser. variable value.

2. Use HTML form

Use HTML form to transfer data from HTML to PHP. Define name and value attributes in the form, and submit the form data to the PHP file. For example, the following HTML code can pass the username and password entered by the user to PHP:

<form action="login.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="登录">
</form>

In PHP, you can use the $_POST super global variable to receive submitted form data. For example, the following PHP code can output the username and password variables in the form:

<?php
$username = $_POST["username"];
$password = $_POST["password"];
echo "Username: " . $username . "<br>";
echo "Password: " . $password . "<br>";
?>

When receiving data in the form, you need to pay attention to guard against security issues such as cross-site scripting attacks (XSS) and SQL injection, such as using htmlspecialchars Handle HTML special characters in forms, use mysqli_real_escape_string to prevent SQL injection, etc.

3. Using PHP session

Using PHP session can share data between two pages. This value transfer method is suitable for user login, shopping cart and other scenarios. In PHP, session is an array variable that saves user information. You can open a session through the session_start() function. Use the session_id() function in other PHP files to get the current session id, and call the $_SESSION super global variable. To read and modify data in the session. For example, the following code can save logged-in user information into the session:

<?php
session_start();
$username = "testuser";
$_SESSION["username"] = $username;
?>

In other PHP files, the data in the session can be obtained through the following code:

<?php
session_start();
$username = $_SESSION["username"];
echo "Welcome user " . $username;
?>

It should be noted that, The session is stored on the server, so the security and integrity of the data need to be ensured, such as opening an HTTPS connection, checking the validity period of the session ID, etc.

Summary

The above three methods can all be used to pass values ​​from PHP to HTML, but each has different usage scenarios and precautions. Developers need to choose the appropriate solution based on needs and security considerations. At the same time, you also need to pay attention to details such as variable naming conventions and data type matching to ensure the stability and maintainability of the code.

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