如何使用PHP中的函数获取数据？ [重复]

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I have this function in functions.php and I want to fetch data using this function

function getQuestionByNumber($number){
        $sql = "SELECT * FROM question WHERE id = '$number'";
        $result = mysqli_query($db, $sql);
        $row = mysqli_fetch_assoc($result);
        return $row;
    }

What I am trying to do is using this function I want to fetch question from question table on the test page Heres my test page code:

<?php
    include('includes/conn.php');
    include('includes/functions.php');

    $number = $_GET['num'];
    $ques = getQuestionByNumber($number);
?>

<textarea readonly><?php echo $ques['question']; ?></textarea>

But it is giving error:

Notice: Undefined variable: db in C:\xampp\htdocs\onlineExam\testingques.php on line 9
Warning: mysqli_query() expects parameter 1 to be mysqli, null given in C:\xampp\htdocs\onlineExam\testingques.php on line 9
Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, null given in C:\xampp\htdocs\onlineExam\testingques.php on line 10

Can someone please help me I am a beginner and just started building applications

</div>

try do something like

function getQuestionByNumber($db, $number)