我的pdo错误如果声明

Question

I want to add to database user_id and fav_id. But only if they both together are not recorded yet. I did something wrong in my code becayse it all the time adds it. Why does that happen?

<?php
include '../connect.php';

$fav_id = $_POST['fav_id'];
$user_id = $_POST['user_id'];

$number = $pdo-> query('SELECT COUNT(*) FROM favourites WHERE user_id = :user_id AND fav_id = fav_id ');

if ($number == 0) {
$pdo->exec("INSERT INTO `favourites` (`fav_id`, `user_id`) VALUES (" . $fav_id . "," . $user_id . ")");
}
else die();

?>

Answer 1

use fetchColumn()

more over i think you should be preparing the statement with :user-id and fav_id

<?php
include '../connect.php';

$fav_id = $_POST['fav_id'];
$user_id = $_POST['user_id'];

$number = $pdo-> prepare('SELECT COUNT(*) FROM favourites WHERE user_id = :user_id AND fav_id = :fav_id ');

$number ->execute(array(':user_id' => $user_id,':fav_id'=>$fav_id));

if ($number ->fetchColumn() == 0) {
$pdo->exec("INSERT INTO `favourites` (`fav_id`, `user_id`) VALUES (" . $fav_id . "," . $user_id . ")");
}
else die();

?>