<?php
function countusers($connection, $column, $table)
{
    $stmt = mysqli_prepare($connection, "
                                    SELECT
                                        COUNT($column)
                                    FROM
                                        $table");
    if($stmt)
    {
        mysqli_stmt_bind_result($stmt, $num);
        mysqli_execute($stmt);
        mysqli_stmt_fetch($stmt);
        mysqli_stmt_close($stmt);
    }
    return $num;
}

<?php
require_once "conn.php";
include "func.php";
echo countusers($conn, "id", "mods");

<?php
$conn = mysqli_connect("localhost", "root", "", "test", 3306);
if(!$conn)
{
    echo "An Error Occurred";
}

//... SNIP...
    if($stmt)
    {
        mysqli_stmt_execute($stmt); // Changed this to  mysqli_stmt_execute
        mysqli_stmt_bind_result($stmt, $num);
        mysqli_stmt_fetch($stmt);
        mysqli_stmt_close($stmt);
    }
    return $num;
// ... SNIP ...