Undefined variable: the_post_id and Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, boolean

Question

Notice: Undefined variable: the_post_id in C:\xampp\htdocs\renda\post.php on line 27

Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, boolean given in C:\xampp\htdocs\renda\post.php on line 30

This is line 27

$query ="SELECT * FROM posts WHERE post_id = {$the_post_id}";

This is line 30

while ($row = mysqli_fetch_assoc($select_all_posts_query)) {

This is my PHP Code

<?php

if(isset($_GET['p_id'])) {
    $the_post_id = $_GET['p_id'];
}


$query ="SELECT * FROM posts WHERE post_id = {$the_post_id}";
$select_all_posts_query = mysqli_query($connection, $query);

while ($row = mysqli_fetch_assoc($select_all_posts_query)) {
    $post_id = $row['post_id'];
    $post_title = $row['post_title'];
    $post_author = $row['post_author'];
    $post_date = $row['post_date'];
    $post_image = $row['post_image'];
    $post_content = $row['post_content'];

1st check whether you are getting any parameters in `$_GET` 2nd your connection string is missing. — Apb, Feb 29 '16 at 09:51
Please read [What topics can I ask about](http://stackoverflow.com/help/on-topic) and [How to ask a good question](http://stackoverflow.com/help/how-to-ask) And [the perfect question](http://codeblog.jonskeet.uk/2010/08/29/writing-the-perfect-question/) — RiggsFolly, Feb 29 '16 at 09:53
Show us the HTML for your `
` or `` tag. We need to know what you think you are passing to the script in $_GET — RiggsFolly, Feb 29 '16 at 09:55
`$_GET['p_id']` is not set here and query executed.... `print_r($_GET['p_id']);` — devpro, Feb 29 '16 at 09:57
Also add a `print_r($_GET);` to the top of this script and then show us what it returns — RiggsFolly, Feb 29 '16 at 09:58
@Dharman just to explain myself: there are several dupe targets but I choose the most important one in my opinion. I don't also want to edit the list as not to distract the attention form the main problem. — Your Common Sense, Oct 31 '19 at 05:08

score -1 · Answer 1 · answered Feb 29 '16 at 09:58

The first "notice" error can be prevented by not executing all the code if p_id isn't present. The second error is because mysqli_query can return false (see the PHP documentation for the function).

I would probably do something like this:

<?php

    if (isset($_GET['p_id'])) {

        $the_post_id = $_GET['p_id'];

        $query = "SELECT * FROM posts WHERE post_id = $the_post_id";
        $select_all_posts_query = mysqli_query($connection, $query);

        if ($select_all_posts_query) {
            while ($row = mysqli_fetch_assoc($select_all_posts_query)) {
                $post_id = $row['post_id'];
                $post_title = $row['post_title'];
                $post_author = $row['post_author'];
                $post_date = $row['post_date'];
                $post_image = $row['post_image'];
                $post_content = $row['post_content'];
            }
        }
        else {
            // handle error condition (the query failed)
        }
    }
    else {
        // handle p_id not being in $_GET
    }

?>

Undefined variable: the_post_id and Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, boolean

1 Answers1