$ _GET值为空isset if语句

Question

I am creating a messaging system and storing the message on to a database from a form.

<form action = "sendmsg.php" method="POST">
            <input type="text" placeholder="Enter subject" name="subject"><br/><br/>
            <textarea style="height:300px;width:450px;" maxlength="50" placeholder="Enter Message" name="message"></textarea><br/><br/>
            <input type="submit" name="submitmsg" value="Send Message"/>
            <?php
            require("dbcon.php");

            if(isset($_POST['submitmsg'])){
                $to = $_GET['id']; 
                $subject = $_POST['subject'];
                $message = $_POST['message'];
                $sql = "INSERT INTO msg VALUES ('','$to','NOW()','$subject','$message')";
                $send = mysqli_query($con, $sql);
                echo "Done";
                echo $to;
            }

My problem here is once the submit button has been selected, the $_GET['id'] value is empty. The sql query executes but $_GET['id'] is empty. I have tried various ways to get the $_GET['id'] to work like using a double if statement to check $_GET and $_POST but that didn't work anyway.

I am kinda new to php and been doing this on and off basis.

Any suggestions?

Answer 1

You are sending in the data via the form but you are not sending in any URI information for the $_GET array to parse. Also I am assuming that the HTML and PHP are on separate pages if not you will have to do PHP_SELF as your action to post back to itself properly.

You will need to add this to your form action

?id=<?php echo $id ?>

Like so:

<form action = "sendmsg.php?id=<?php echo $id ?>" method="POST">
        <input type="text" placeholder="Enter subject" name="subject"><br/><br/>
        <textarea style="height:300px;width:450px;" maxlength="50" placeholder="Enter Message" name="message"></textarea><br/><br/>
        <input type="submit" name="submitmsg" value="Send Message"/>
        <?php
        require("dbcon.php");

        if(isset($_POST['submitmsg'])){
            $to = $_GET['id']; 
            $subject = $_POST['subject'];
            $message = $_POST['message'];
            $sql = "INSERT INTO msg VALUES ('','$to','NOW()','$subject','$message')";
            $send = mysqli_query($con, $sql);
            echo "Done";
            echo $to;
        }