Performance on PHP sql queries

I'm barely learning PHP and MYSQL so I don't know much about performance, I've wrote this script to fetch and format content from my DB, it also counts how many result are and separate them in to pages. I would appreciate your feedback n.n

function fetch_content($section, $subsection, &$count, $page = 0){
    $section = substr($section, 0,8);
    $subsection = substr($subsection, 0,8);
    require_once("system/config.php");
    //Initiate connection 
        $mysqli = new mysqli($db_host, $db_user, $db_password, $db_database);
        if ($mysqli->connect_error) {
            die('Connect Error (' . $mysqli->connect_errno . ') '. $mysqli->connect_error);
        }
    //Select page
        $limit = 2;
        $start = $page * $limit ;

    //select query
        if($section == 'home' || ($section != 'home' && $subsection == NULL)){
            $selection =  "WHERE section = ?";
            }
        else
            $selection = "WHERE section = ? AND subsection = ?";

    //Fetch data
        $stmt = $mysqli->stmt_init();
        $qry= "SELECT * FROM public
        $selection
        ORDER BY id DESC LIMIT ?,?";
        $stmt->prepare($qry);
        if($section == 'home' || ($section != 'home' && $subsection == NULL))
            $stmt->bind_param("sss", $section, $start , $limit);
        else
            $stmt->bind_param("ssss", $section, $subsection, $start , $limit);
        $stmt->execute();
        $result = $stmt->get_result();
    //Format the data
        while( $row =  $result->fetch_assoc()){
            format_home($row, $mysqli);
        }
        $stmt->close();
    //Count result
        $stmt = $mysqli->stmt_init();
        $qry= "SELECT COUNT(*) AS count FROM public  $selection";
        $stmt->prepare($qry);
        if($section == 'home' || ($section != 'home' && $subsection == NULL))
            $stmt->bind_param("s", $section);
        else
            $stmt->bind_param("ss", $section, $subsection);
        $stmt->execute();
        $result = $stmt->get_result();
        $count = $result->fetch_assoc();
        $count =  $count['count'];
        $stmt->close();
    //close connection
        $mysqli->close();
}