What is a hidden field? Let's talk about its application in PHP blogs

Hidden fields are a very important concept in PHP development. When developing dynamic websites, hidden fields are often used to pass data between pages, such as login status, form data, etc. In this article, we will explore what hidden fields are, how to use them, and their applications in PHP blogging.

What is a hidden domain?

Hidden fields are HTML form elements that are used to save data in web pages. These data are invisible but can be accessed by server-side script code. When a form is submitted, data is sent to the server, including all visible and hidden form elements. In PHP, you can use the $_POST and $_GET global arrays to obtain the passed form data.

How to use hidden fields?

The first step in using hidden fields is to define the HTML form. Here is a simple example:

<form method="post" action="form_action.php">
  <input type="text" name="name" value="" placeholder="请输入您的名字">
  <input type="password name="password" value="" placeholder="请输入您的密码">
  <input type="hidden" name="hidden1" value="这是隐藏的表单元素">
  <input type="submit" name="submit" value="提交">
</form>

In the form above, there are two visible text input boxes and a hidden field. The name of this hidden field is "hidden1" and its value is "This is a hidden form element". When the user clicks the submit button, the value of this hidden field will be passed to the server along with the form data.

How to use hidden fields in PHP blog?

Hidden domains can play an important role when developing a PHP blog. Here is an example of how to use hidden fields to add comments to an article:

1. Define Comment Form

<form method="post" action="add_comment.php">
  <input type="text" name="name" value="" placeholder="请输入您的名字">
  <textarea name="comment" placeholder="请输入您的评论"></textarea>
  <input type="hidden" name="post_id" value="<?php echo $post_id; ?>">
  <input type="submit" name="submit" value="提交">
</form>

In this comment form, we have defined three forms The elements are "name", "comment" and "post_id". Among them, "post_id" is the hidden field we defined, and its value is the ID of the current article. When the user submits a comment, the value of this hidden field will be passed to the background script add_comment.php.

2. Processing comment form data

// add_comment.php

// Get form data
$name = $_POST['name'];
$comment = $_POST['comment'];
$post_id = $_POST['post_id'];

// Insert data into the database
$stmt = $pdo->prepare("INSERT INTO comments (name, comment, post_id)

                     VALUES (?, ?, ?)");

$stmt->execute([$name, $comment, $post_id]);

// Jump to the article details page after successful submission
header("Location: post.php?id=$post_id");
?>

In add_comment. In php, we use PHP's PDO extension to insert comment data into the database. Notice here that we get the ID of the current article from the hidden field and insert it into the comments table. Finally, we use the header() function to jump Return to the article details page.

3. Display comments

In the article details page, we can use the following code to display the comment list:

// post.php

// Get article ID
$id = $_GET['id'];

// Get article data
$ stmt = $pdo->prepare("SELECT * FROM posts WHERE id = ?");
$stmt->execute([$id]);
$post = $stmt->fetch( );

// Get the comment list
$stmt = $pdo->prepare("SELECT * FROM comments WHERE post_id = ?");
$stmt->execute([$ id]);
$comments = $stmt->fetchAll();
?>

Comments list

> ;

• :

above In the code, we use PHP's PDO extension to get the ID and comment list of the current article from the database. Notice that when obtaining the comment list, we use the ID of the current article as the query condition. Finally, we loop through all the comments.

Summary

Hidden fields are very important in PHP development. They can pass data between pages and the data is invisible. In PHP blog development, we can use hidden fields to add comments to articles and easily associate comments with articles.

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