php pdo query not working with array

Question

I have been doing this for quite a few queries but suddenly found one where it is not working. Here is my code:

$q = 'SELECT title FROM blog LIMIT :paging,:perpage';
$v = array(
    ':paging'=>(($page-1)*$perpage),
    ':perpage'=>$perpage
);
$sql = $conn->prepare($q);
$sql->execute($v);
if ($sql){
    foreach($sql as $rs){
        $title = $rs['title'];
        echo '<article>'.$title.'</article>';
    };
};

I am not getting any errors however It is also not displaying anything. When I take out $v and just put the values into the query like so:

$q = 'SELECT title FROM blog LIMIT '.(($page-1)*$perpage).','.$perpage.' ';

This works perfectly and outputs fields.

I have does this same array trick on many other queries in the past and never had any problems. Not sure what I did wrong here, need a fresh pair of eyes.

also $page = 1 and $perpage = 2

Answer 1

Its because when you use an array for execute, it defaults to PDO::PARAM_STR , so it thinks its a string...which obviously doesn't play well with LIMIT

Instead use bindValue , that way you can explicitly state PDO::PARAM_INT

 $q = 'SELECT title FROM blog LIMIT :paging,:perpage';
 $sql = $conn->prepare($q);

 $sql->bindValue(':paging',(($page-1)*$perpage), PDO::PARAM_INT);
 $sql->bindValue(':perpage',$perpage, PDO::PARAM_INT);
 $sql->execute();

Answer 2

You need to use bindValues to bund the values to the query the use execute with no parameters!

http://php.net/manual/en/pdostatement.bindvalue.php

Answer 3

You're not getting any PHP errors but you're not checking for SQL errors at all. You need to explicitly check for SQL errors.

try {
    $dbh = new PDO($dsn, $user, $password);
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    echo 'Connection failed: ' . $e->getMessage();
}