Staż,praktyki PHP

if(isset($_GET['category'])){
    include "php/db_connect.php";
    try{
        $result=$pdo->query("SELECT * FROM category");
    }catch (PDOException $e){
        $error="Błąd cat ".$e->getMessage();
        include "html/error.html.php";
        exit();
    }
    foreach ($result as $row){
        $category[]=array('id'=>$row['id'],'title'=>$row['title_category']);
    }
    try{
        $sql=("SELECT post.id,post.day,post.month,post.title,post.text,post.likes,post.comments,post.img,category.title_category FROM ((post_category INNER JOIN post on post_category.post_id=post.id) INNER JOIN category on post_category.category_id=category.id) WHERE category.id = :category_id");
        $s=$pdo->prepare($sql);
        $s->bindValue('category_id',$_GET['category']);
        $s->execute();
    }catch (PDOException $e){
        $error="Błąd cat: ".$e->getMessage();
        include "html/error.html.php";
        exit();
    }
    foreach ($s as $row) {
        $posts[] = array('id' => $row['id'], 'day' => $row['day'], 'month' => $row['month'], 'title' => $row['title'], 'text' => $row['text'], 'likes' => $row['likes'], 'comments' => $row['comments'], 'cat' => $row['title_category']);
    }
    include "home.phtml";
    exit();
}
if(isset($_POST['sent'])){
    include "php/db_connect.php";
    $errors=array();
    if($_POST['name'] == ''){
        $errors[]='Wpisz nazwe';
    }
    if($_POST['mail'] == ''){
        $errors[]='Wpisz mail';
    }
    if (preg_match('/([\w\-]+\@[\w\-]+\.[\w\-]+)/', $_POST['mail'])){
    }else{
        $errors[]='Wpisz poprawny mail';
    }
    if($_POST['text-comments'] == ''){
        $errors[]='Wpisz text';
    }
    if(empty($errors)){
        try{
            $sql=("UPDATE post SET comments=comments+1 WHERE id=:pid");
            $s=$pdo->prepare($sql);
            $s->bindValue(':pid',$_POST['hidden']);
            $s->execute();
        }catch (PDOException $e){
            $error="Błąd up: ".$e->getMessage();
            include "html/error.html.php";
            exit();
        }
        try{
            $sql=("INSERT INTO comments SET name = :name, email = :email, comment = :comment, id_post = :id_post, data = NOW()");
            $s=$pdo->prepare($sql);
            $s->bindValue(':name',$_POST['name']);
            $s->bindValue(':email',$_POST['mail']);
            $s->bindValue(':comment',$_POST['text-comments']);
            $s->bindValue(':id_post',$_POST['hidden']);
            $s->execute();
        }catch (PDOException $e){
            $error="Błąd ad: ".$e->getMessage();
            include "html/error.html.php";
            exit();
        }
        header('Location: /YKozhemiaka_Blog/?id='.$_POST['hidden']);
        exit();
    }else{

    }
}
if(isset($_GET['next'])){
    include "php/db_connect.php";
    try{
        $sql=("SELECT post.id,post.day,post.month,post.title,post.text,post.likes,post.comments,post.img,category.title_category FROM ((post_category INNER JOIN post on post_category.post_id=post.id) INNER JOIN category on post_category.category_id=category.id) WHERE post.id=:pid+1");
        $s=$pdo->prepare($sql);
        $s->bindValue(':pid',$_GET['next']);
        $s->execute();
    }catch (PDOException $e){
        $error="Błąd pag: ".$e->getMessage();
        include "html/error.html.php";
        exit();
    }
    foreach ($s as $result) {
        $posts_id[] = array('id'=>$result['id'],'title' => $result['title'], 'text' => $result['text'],'likes'=>$result['likes'],'comments'=>$result['comments'],'img'=>$result['img'],'cat'=>$result['title_category']);
    }
    try{
        $result=$pdo->query("SELECT * FROM category");
    }catch (PDOException $e){
        $error="Błąd cat: ".$e->getMessage();
        include "html/error.html.php";
        exit();
    }
    foreach ($result as $row){
        $category[]=array('id'=>$row['id'],'title'=>$row['title_category']);
    }
    try{
        $sql=("SELECT * FROM comments WHERE id_post = :id_post+1 ORDER BY data DESC");
        $s=$pdo->prepare($sql);
        $s->bindValue(':id_post',$_GET['next']);
        $s->execute();
    }catch (PDOException $e){
        $error="Bład com: ".$e->getMessage();
        include "html/error.html.php";
        exit();
    }
    foreach ($s as $row){
        $comments[]=array('name'=>$row['name'],'text'=>$row['comment']);
    }    try{
        $result=$pdo->query('SELECT id FROM post ORDER BY id DESC LIMIT 1');
    }catch (PDOException $e){
        $error="Błąd cat: ".$e->getMessage();
        include "html/error.html.php";
        exit();
    }
    foreach ($result as $row){
        $last_id[]=array('id'=>$row['id']);
    }
    foreach ($last_id as $last){
        $lasting=$last['id'];
    }
    include "single.phtml";
    exit();
}