mysqli_query("SELECT email, passwd, login_id, full_name FROM members WHERE email = 'x'; DROP TABLE members; --'");

<?php
    // Prevent errors from showing
    error_reporting(0);
    // Connect the db
    require '../../connect_db.php';

    if (isset($_POST['UserName'], $_POST['UserPass'] ) ) {

        // Grab user Input
        $UserName = $_POST['UserName'];
        $UserPass = $_POST['UserPass'];

        // The passwords in this case are stored in the clear. This is an early example.
        // BINARY is used to force matching case.
        $query = "SELECT * FROM users WHERE UserName='".$UserName."' AND BINARY UserPass='".$UserPass."'";

        $result = mysqli_query($db, $query)
         or die("Error: " . mysqli_error($db));


        // Echo out the table row(s)
        while($row = mysqli_fetch_array($result)) {
            echo '<tr class="query-result">'; // Class is added so that jQuery can remove old ones
            echo '<td>' . $row['UserId'] . '</td>';
            echo '<td>' . $row['UserName'] . '</td>';
            echo '<td>' . $row['UserPass'] . '</td>';
            echo '<td>' . $row['UserRole'] . '</td>';
            echo '</tr>';
        }
    }