檢查項

Question

我想測試中user_saved表是否存在一個特定的UID MID和條目，所以這裏就是我所做的

$result = $db->prepare("SELECT * FROM user_saved WHERE UID = ? AND MID = ?"); 
      $result->execute(array($_SESSION['uid'], $itemId['MID2'])); 
      $test = $result->fetch(PDO::FETCH_ASSOC); 
       if (isset($test)){ 
     exist 
     } else { 
        doesn't exist 
       } 

的問題是，我想使用不存在的UID和MID，但它總是進入isset語句，爲什麼？有什麼更好的方法來做到這一點？

Answer 1

isset檢查變量是否存在或不使用strlen函數或陣列計數功能

<?php 
$bbnq = sprintf("SELECT login 
FROM users 
WHERE id = %u",27); 
try 
    { $req = $db_bbn->query($bbnq); } 
catch (Exception $e) 
    { bbnf_pdo_error($e,__FILE__,__LINE__); } 
if ($r = $req->fetch()) 
    { echo "This query has a row result"; } 
else 
    { echo "This query has an empty result"; } 
?> 

Answer 2

fetch returns FALSE on failure：

if ($test !== FALSE) // ...