如何有效地替换PDO中的（mysql_result（mysql_query（））？

Question

As my process is almost complete for rewriting web with PDO instead of mysql_* commands I am now testing my changed functions. And It seems that my changed function for mysql_result(mysql_query() always returns true, why is that? Lets see original and changed code:

if (mysql_result(mysql_query("SELECT COUNT(*) FROM account WHERE id='".$_SESSION["user_id"]."' AND online=1"), 0)>0)
{
  return true; 
}
else
  return false;

And changed code here:

$stmt = $db_login->prepare("SELECT COUNT(*) FROM account WHERE id=:id AND online=1");
$stmt->bindValue(':id', $_SESSION["user_id"], PDO::PARAM_INT);
$stmt->execute();
$results_login = $stmt->fetch(PDO::FETCH_ASSOC);
$rows = count($results_login);
if ($rows > 0)
{
  return true; 
}
else
  return false;

So what is wrong with is why it always returns true even when column has online=0? Thank you

Answer 1

$stmt->fetch fetches one row from the result set. What you get out of that is an array containing all the selected columns, looking something like this:

array(
    'COUNT(*)' => 42
)

A count() on that array will always result in 1 .

You need to check the contents of the fetched row:

if ($result_login['COUNT(*)'] > 0)

It's best to alias this column to a nicer name:

SELECT COUNT(*) AS `count` ...

Then:

if ($result_login['count'] > 0)