Fatal error : Uncaught PDOException: SQLSTATE[42000] [closed] - php

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<?php
class dblib {
private $__conn;
function connect(){
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "webtintuc";
if (!$this->__conn){
try {
$this->__conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
$this->__conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e){
echo "Error: " . $e->getMessage();
die();
}
}
}
function dis_connect(){
if ($this->__conn){
$this->__conn = null;
}
}
function insert($table, $data)
{
$this->connect();
$field_list = '';
$value_list = '';
foreach ($data as $key => $value){
$field_list .= ",$key";
$value_list .= ",'".$value."'";
}
$sql = 'INSERT INTO '.$table. '('.trim($field_list, ',').') VALUES ('.trim($value_list, ',').')';
$stmt = $this->__conn->prepare($sql);
return $stmt->execute();
}
function update($table, $data, $where){
$this->connect();
$sql = '';
foreach ($data as $key => $value){
$sql .= "$key = '".$value."',";
}
$sql = 'UPDATE '.$table. ' SET '.trim($sql, ',').' WHERE '.$where;
$stmt = $this->__conn->prepare($sql);
return $stmt->execute();
}
function remove($table, $where){
$this->connect();
$sql = "DELETE FROM $table WHERE $where";
$stmt = $this->__conn->prepare($sql);
return $stmt->execute();
}
function get_list($sql){
$this->connect();
$stmt = $this->__conn->prepare($sql);
$stmt->execute();
$stmt->setFetchMode(PDO::FETCH_ASSOC);
return $stmt->fetchALL();
}
function get_row($sql){
$this->connect();
$stmt = $this->__conn->prepare($sql);
$stmt->execute();
$stmt->setFetchMode(PDO::FETCH_ASSOC);
return $stmt->fetch();
}
function get_row_number($sql){
$this->connect();
$stmt = $this->__conn->prepare($sql);
$stmt->execute();
return $stmt->fetchColumn();
}
}
?>
###post.php
<?php
$link = '';
$where = '';
if (isset($_GET["cat"])) {
$cat = intval($_GET["cat"]);
if ($cat != 0)
$where = "WHERE category_id = $cat";
$link = "cat=$cat&";
}
$sql = "SELECT count(*) FROM posts $where";
$total_records = $homelib->get_row_number($sql);
$limit = 3;
$current_page = isset($_GET['page']) ? $_GET['page'] : 1;
$total_page = ceil($total_records / $limit);
if ($current_page > $total_page){
$current_page = $total_page;
}
else if ($current_page < 1) {
$current_page = 1;
}
$start = ($current_page - 1) * $limit;
$sql = "SELECT * FROM posts $where ORDER BY createdate DESC LIMIT $start, $limit";
$data = $homelib->get_list($sql);
?>
<!-- Blog Entries Column -->
<div class="col-md-8">
<h1 class="my-4">Siêu HOT
<small>tin mới nhất</small>
</h1>
<?php
for ($i = 0; $i < count($data); $i++) {
?>
<div class="card mb-4">
<img class="card-img-top" src="images/<?php echo $data[$i]['image'];?>" height="300px" alt="Card image cap">
<div class="card-body">
<h2 class="card-title"><?php echo $data[$i]['title'];?></h2>
<p class="card-text"><?php echo substr($data[$i]['content'], 0, 200).'...';?></p>
Xem thêm →
</div>
</div>
<?php
}
?>
<!-- Pagination -->
<ul class="pagination justify-content-center mb-4">
<?php
if ($current_page > 1 && $total_page > 1){
echo '<li class="page-item"><a class="page-link" href="index.php?'.$link.'page='.($current_page-1).'">Prev</a></li>';
}
for ($i = 1; $i <= $total_page; $i++) {
if ($current_page == $i)
echo '<li class="page-item disabled"><a class="page-link" href="#">'.$i.'</a></li>';
else
echo '<li class="page-item"><a class="page-link" href="index.php?'.$link.'page='.$i.'">'.$i.'</a></li>';
}
if ($current_page < $total_page && $total_page > 1){
echo '<li class="page-item"><a class="page-link" href="index.php?'.$link.'page='.($current_page+1).'">Next</a></li>';
}
?>
</ul>
</div>
result:
Fatal error
: Uncaught PDOException: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '-3, 3' at line 1 in C:\xampp\htdocs\webtintuc\incs\class_db.php:100 Stack trace: #0 C:\xampp\htdocs\webtintuc\incs\class_db.php(100): PDOStatement->execute() #1 C:\xampp\htdocs\webtintuc\post.php(30): dblib->get_list('SELECT * FROM p...') #2 C:\xampp\htdocs\webtintuc\index.php(8): include('C:\xampp\htdocs...') #3 {main} thrown in
C:\xampp\htdocs\webtintuc\incs\class_db.php
on line
100

Answer 1

The limit and start in an SQL query cannot be negative in any way. It is a number that is used for limiting the number of rows that should be returned by the SQL statement.
To be useful, the limit should always be an integer that is greater than zero. start should be any integer that is zero and up. It is refer to as the offset.
Your calculations are ending up producing a start that is set to -3. That will never work.
Make sure that you review your logic so that it does not produce a negative $start value.
You can quickly confirm my theory by calculating $start like this ...
$start = max(0, ($current_page - 1) * $limit);
This will ensure that the value will be 0 if your formula returns a negative value.
Bear in mind that this is not a permanent solution. You need to properly figure out the way you are computer the value of the $start value.