Call To A Member Function Fetch_object() On A Non-object

Good evening all.
I have written a little "program" that grabs news items and adds them to a MySQL database. Everything is working well. Now I am working on adding functionality that will allow me to add a comment to each item I save - GetEmAll_Comment.php.
My code pulls the existing comments without a problem, but when I submit a new comment I get a strange error message. It is a bit strange because the UPDATE works... but I still get a that strange error. Any ideas?

This is the error message:

( ! ) Fatal error: Call to a member function fetch_object() on a non-object in C:\wamp\www\NewsToolv1\GetEmAll_Comment.php on line 39



GetEmAll_Comment.php:

<?php
 
$id = filter_input(INPUT_POST, 'id', FILTER_SANITIZE_STRING);
$comment = filter_input(INPUT_POST, 'comment', FILTER_SANITIZE_STRING);
 
$existing_comment = '';
 
// Check if the comment was set (posted)
if(isset($comment)){
    addComment($id, $comment);
    echo "record should be added";
} elseif (empty($comment)) {
    $existing_comment = checkForComment($id);
}
 
// Update the database with the new comment
function addComment($id, $comment){
   
    $db = new mysqli('localhost', 'root', '', 'newstoolv1');
    $sql = "UPDATE tbl_news SET clmn_comment='".$comment."' WHERE id=".$id;
    $db->query($sql);
    $db->close();   
   
    // Go back to page
    $callingPage = $_SERVER['HTTP_REFERER'];
    header('location:' . $callingPage);
 
}
 
function checkForComment($id){
   
    $db = new mysqli('localhost', 'root', '', 'newstoolv1');
    $sql = "SELECT * FROM tbl_news WHERE id=".$id;
    $results = $db->query($sql);
    $db->close();
   
    $r = '';
   
    while($output_item = $results->fetch_object()){
        $r = $output_item->clmn_comment;
    }
   
    return $r;
   
}
 
 
?>
 
<form class="form" method="POST" action="GetEmAll_Comment.php">
<input type="hidden" name="id" value="<?PHP echo $id;?>">
<textarea rows="1" cols="60" name="comment"><?PHP echo $existing_comment;?></textarea>
<input type="submit" value="Submit">
</form>

PHP:

 

I think you wrote a wrong statement on line no. 39

It should be

while($output_item = $db->fetch_object()){
 
        $r = $output_item->clmn_comment;
 
    }

PHP:

 

At line 34, try

$result = $mysqli->query($sql) {

PHP:

 

Thank you for the help.

Interesting, it seems as though the form post doesn't work, or the POST values are not captured. They show up as empty, in which case the SQL query can't run correctly.

I've tried to separate the form code a bit.

<?php
 
$id = filter_input(INPUT_POST, 'id', FILTER_SANITIZE_STRING); //  Gets passed in from GetEmAll.php via form POST
 
// Gets passed form this file "GetEmAll_Comment.php" via form POST
$id_form = filter_input(INPUT_POST, 'id_form', FILTER_SANITIZE_STRING);
$comment_form = filter_input(INPUT_POST, 'comment_form', FILTER_SANITIZE_STRING);
 
 
echo "id: ".$id."<br/>";
// echo "comment: ".$comment."<br/>";
echo "id_form: ".$id_form."<br/>";
echo "comment_form: ".$comment_form."<br/>";
 
 
 
// Check if the comment was set (posted)
if(isset($comment_form) && isset($id_form)){
   
    // if both $comment_form and $id_form are set it must be submitted from the form
    // if it is submitted from the form, update the database record
    addComment($id_form, $comment_form);
    echo "added: ".$comment_form." to ".$id."<br />";
   
} else {
    $existing_comment = checkForComment($id);
}
 
// Update the database with the new comment
function addComment($id, $comment){
   
    $db = new mysqli('localhost', 'root', '', 'newstoolv1');
    $sql = "UPDATE tbl_news SET clmn_comment='".$comment."' WHERE id=".$id;
    $db->query($sql);
    $db->close();   
 
    // Go back to page
    $callingPage = $_SERVER['HTTP_REFERER'];
    header('location:' . $callingPage);
 
}
 
function checkForComment($id){
   
    echo "checkForComment() Function<br/>";
    echo "id: ".$id."<br/>";
   
    $db = new mysqli('localhost', 'root', '', 'newstoolv1');
    $sql = "SELECT * FROM tbl_news WHERE id=".$id;
    $results = $db->query($sql);
    $db->close();
   
    echo "The SQL statement:<br/>";
    echo "sql var: ".$sql."<br/>";
   
    var_dump($results);
   
   
    $r = '';
   
    while($output_item = $results->fetch_object()){
        // $r = $output_item->clmn_comment;
        echo "Output from DB".$output_item->clmn_comment."<br/>";
    }
   
    /*
   
    return $r;
    */
}
 
 
?>
 
<form class="form" method="POST" action="GetEmAll_Comment.php">
<input type="hidden" name="id_form" value="<?PHP echo $id;?>">
<textarea rows="1" cols="60" name="comment_form"><?PHP echo $existing_comment;?></textarea>
<input type="submit" value="Submit">
</form>

PHP:

 

Try this:

<?php
if(strlen($_POST['id_form'] == 0) {
 
echo '<form class="form" method="POST" action="GetEmAll_Comment.php">
<input type="hidden" name="id_form" >
<textarea rows="1" cols="60" name="comment_form" />
<input type="submit" value="Submit">
</form>';
exit;
}
 
$id = filter_input(INPUT_POST, 'id', FILTER_SANITIZE_STRING); //  Gets passed in from GetEmAll.php via form POST
 
// Gets passed form this file "GetEmAll_Comment.php" via form POST
$id_form = filter_input(INPUT_POST, 'id_form', FILTER_SANITIZE_STRING);
$comment_form = filter_input(INPUT_POST, 'comment_form', FILTER_SANITIZE_STRING);
 
echo "id: ".$id."<br/>";
// echo "comment: ".$comment."<br/>";
echo "id_form: ".$id_form."<br/>";
echo "comment_form: ".$comment_form."<br/>";
 
// Check if the comment was set (posted)
if(isset($comment_form) && isset($id_form)){
 
    // if both $comment_form and $id_form are set it must be submitted from the form
    // if it is submitted from the form, update the database record
    addComment($id_form, $comment_form);
    echo "added: ".$comment_form." to ".$id."<br />";
 
} else {
    $existing_comment = checkForComment($id);
}
 
// Update the database with the new comment
function addComment($id, $comment){
 
    $db = new mysqli('localhost', 'root', '', 'newstoolv1');
    $sql = "UPDATE tbl_news SET clmn_comment='".$comment."' WHERE id=".$id;
    $db->query($sql);
    $db->close();
 
    // Go back to page
    $callingPage = $_SERVER['HTTP_REFERER'];
    header('location:' . $callingPage);
 
}
 
function checkForComment($id){
    echo "checkForComment() Function<br/>";
    echo "id: ".$id."<br/>";
 
    $db = new mysqli('localhost', 'root', '', 'newstoolv1');
    $sql = "SELECT * FROM tbl_news WHERE id=".$id;
    $results = $db->query($sql);
    $db->close();
 
    echo "The SQL statement:<br/>";
    echo "sql var: ".$sql."<br/>";
 
    var_dump($results);
 
    $r = '';
 
    while($output_item = $results->fetch_object()){
        // $r = $output_item->clmn_comment;
        echo "Output from DB".$output_item->clmn_comment."<br/>";
    }
 
    /*
 
    return $r;
    */
}
 
?>

PHP:

The way you did it, the PHP code ran, then created the form and sent it to the user. There was nothing submitted yet, so the code was running with no POST values. (I didn't check the rest of the code, just the fact that you were running the PHP code by connecting to the site, not by submitting the form.) BTW, you can't fill the values into the form before you submit the form.

(You do understand how client-server works, right? When you connect to the site, the server-side code runs. The client-side code doesn't exist until the server-side code sends the client-side code [like the form] to the client. You can't just mix them together - they're not running at the same time, or in the same place.)

 

Thank you, you are on-to something.

When the page loads, it has 1 value to start with, which is passed in from GetEmAll.php, it is the ID of the news item. If the "id" is set, I want to see if there is already a comment to that news item i the database, if there is, I want to pull it out and populate the text area (checkForComment($id)).

The problem occurs when checkForComment($id) is executed after the form was submitted, there is no $id_form value set, for some reason.

If I remove

// Go back to page
$callingPage = $_SERVER['HTTP_REFERER'];
header('location:' . $callingPage);

PHP:

Then it works great, it just doesn't go back to the GetEmAll.php page. But I solved that by passing through the referring page

 

Check the value of $id right at the top of the file (after line 3 in your first post). If it's blank there after submitting the form, a value for $id isn't being POSTed by the calling file (or the value is blank).