我收到这条消息，为什么？ mysqli_query（）：无法获取mysqli [重复]

Question

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• Warning: mysqli_query(): Couldn't fetch mysqli 2 answers
• mysqli::query(): Couldn't fetch mysqli 4 answers

This is the connection page, and it works well with my index file. Now the question is: I need another sql to be run on another page where it is supposed to go like this: SELECT * FROM products WHERE id = $var. But it gives me "mysqli_query(): Couldn't fetch mysqli" when I try to do it, what should I do?

connection.php

$host = "localhost";
$dbusername = "root";
$dbpassword = "";
$db = "movies";

//connecting to the database
$conn = mysqli_connect("$host","$dbusername","$dbpassword","$db");
mysqli_set_charset($conn,'utf8');

//check for error in connection
if (!$conn) {
  die ('Failed to connect to MySQL: ' . mysqli_connect_error());
}

//Selecting table and executing query
$sql = 'SELECT * FROM products';
$query = mysqli_query($conn, $sql);

if (!$query) {
  die ('SQL Error: ' . mysqli_error($conn));
}

mysqli_close($conn);

-- another page--

<?php

include "connection.php";

$movieid = $_GET['movieid'];

$sql = 'SELECT * FROM products WHERE id = "$movieid"';
$query = mysqli_query($conn, $sql);

$movie_title = $row['title'];
echo "$movie_title";
?>

</div>

Answer 1

The reason for this error is because you are closing the connection on your connenction.php file. You just need to remove this line:

mysqli_close($conn);