Please I want to Restructure this php URL to SEO friendly URL [duplicate]

Question

I have this is the listing page: <div class="group"><a href="/category?id=<?php echo $data->slug;?>"><?php echo $data->title; ?></a></div>

I have this https://example.com/category/?id=slug

but I want this https://example.com/category/slug-id

Then I have this in the /category/index.php

if(get_magic_quotes_gpc())
    {$uid = htmlentities(stripslashes(strip_tags(trim($pid))));}
try {$stmt = $db->prepare("select * from answers where ans_slug =:pid");
        $stmt->execute(array(':pid' => $pid));
            $row = $stmt->fetch(); 
        } catch(PDOException $e) {
            echo $e->getMessage();
        }
if($row['ans_slug'] == '' || empty($pid)){
    header('Location: ./');
    exit;
}

Please help