如何使用php插入MySQL并回显它

Question

I'm really new to PHP and need some help.

I want to build a forum where you can upload posts and pictures.

Now, I need help with the connection between my code and my MySQL database.

I'm using MySQL with the folowing table:

main table: "posts"

1. post_data = it's an POST request from the user.
2. username = from another main table: users
3. user_id = from another main table: users
4. post_id = Automatic .

I want to post the data that I get from the user and I don't really know what the problem is.

This is the PHP code:

<?php

session_start();
$MySQLdb = new PDO("mysql:host=127.0.0.1;dbname=forum", "root", "");
$MySQLdb->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

 if(isset($_POST['msg'])){

     $post   = $_POST['msg'];

     $cursor = $MySQLdb->prepare("SELECT post_data FROM posts WHERE post=:posts_data");
     $cursor->execute( array(":post_data"=>$post) );
 }
$cursor = $MySQLdb->prepare("INSERT INTO posts (post) value (:post_data)");
$cursor->execute(array(":post_data"=>$post));?>

and this is the HTML code for "msg" (the post input):

div class="input-group">
                <input id="msg" type="text" method="POST" class="form-control" name="msg" placeholder="Write your message here...">
                <span class="input-group-addon"><button id="send_post">Send</button></span>
            </div>

This is the error that I get:

Notice: Undefined variable: post in C:\\xampp\\htdocs\\forum\\main.php on line 15

Fatal error: Uncaught PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'post' in 'field list' in C:\\xampp\\htdocs\\forum\\main.php:15 Stack trace: #0 C:\\xampp\\htdocs\\forum\\main.php(15): PDOStatement->execute(Array) #1 {main} thrown in C:\\xampp\\htdocs\\forum\\main.php on line 15

Thanks a lot.

Answer 1

Your html is all wrong.

        <input id="msg" type="text" method="POST" class="form-control" name="msg" placeholder="Write your message here...">

The method is an attribute on form tag, not input.

<form action="/youraction" method="POST" />
<input id="msg" type="text" method="POST" class="form-control" name="msg" placeholder="Write your message here...">
</form>

PHP fails because there's no $_POST['msg'] set

Answer 2

Perhaps method your html form is get or ...

Change $_POST['msg']; to $_REQUEST['msg'];

<?php

session_start();
$MySQLdb = new PDO("mysql:host=127.0.0.1;dbname=forum", "root", "");
$MySQLdb->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
 $post   ="";
 if(isset($_REQUEST['msg'])){

     $post   = $_REQUEST['msg'];

     $cursor = $MySQLdb->prepare("SELECT post_data FROM posts WHERE post=:posts_data");
     $cursor->execute( array(":post_data"=>$post) );
 }
$cursor = $MySQLdb->prepare("INSERT INTO posts (post) value (:post_data)");
$cursor->execute(array(":post_data"=>$post));?>

Answer 3

Which of the lines is Line 15? is it the $cursor = $MySQLdb->prepare("INSERT INTO posts (post) value (:post_data)");

Because if it so then you might want to find a way of SETTING you $post variable. Take a look at your code, you are setting $post inside the if(){} statement and so when it tries to execute the below lines:

$cursor = $MySQLdb->prepare("INSERT INTO posts (post) value (:post_data)");
$cursor->execute(array(":post_data"=>$post));?>

Your $post variable is empty.

Answer 4

"INSERT INTO posts (post) value (:post_data)" must be changed to "INSERT INTO posts (post_data) value (:post_data)" .

Please be aware, that there might come new MySQL errors depending on your table definition and the defined constraints.