PHP PDO query not returning any data, isset() showing data is returned

Question

I have some basic php code which attempts to authenticate against a username and password in a database. It is supposed to print "Authenticated" if there is a successful match of user & pass. However, the query is not returning any data. In addition, the isset() I am using to check if any data is returned shows that the array has values in it.

What is going wrong here, how can I get this pdo query to return the requested data?

Here is the code with issues.

    $stmt = $pd->prepare("SELECT username from users where username = :logon and password = :passwd");
    $stmt->bindParam(':logon', $_POST['username'], PDO::PARAM_STR);
    $stmt->bindParam(':passwd', $_POST['password'], PDO::PARAM_STR);
    $stmt->execute();
    $verify_auth = $stmt->fetchAll();
    if(isset($verify_auth)){
       echo "Authenticated locally";
       $authed = 1;
       //do something here
    }
    elseif($authed != 1){
        echo "<b>Failure to authenticate</b>";
    }

Every time it runs "Authenticated locally" even though the credentials are wrong.

The verify_auth array appears to always be empty even with the correct credentials.

The post parameters are being assigned successfully.

PDOStatement::fetchAll Return values: php.net/manual/en/… — Saleh Mahmood
– Saleh Mahmood, Commented Oct 24, 2019 at 17:52

Andrey Kostenko · Accepted Answer · 2019-10-24 19:41:33Z

1

fetchAll() always returns an array, you need to check if it's not empty instead. Also you set $authed to 1 after checking for $verify_auth and it turns out, the last condition block (in case if $authed != 1) will never be executed. Instead you can make it useful through simple else. Here's the example what it would look like.

$stmt = $pd->prepare("SELECT username from users where username = :logon and password = :passwd");

$stmt->bindParam(':logon', $_POST['username'], PDO::PARAM_STR);
$stmt->bindParam(':passwd', $_POST['password'], PDO::PARAM_STR);
$stmt->execute();
$verify_auth = $stmt->fetchAll();

if ($verify_auth) {
  echo "Authenticated locally";
  $authed = 1;
  //do something here
} else {
  echo "<b>Failure to authenticate</b>";
}

isset() is very useful, but not in this particular case. It checks is variable set, so even if it has an empty value it will be set and isset() would give you true. But if there's a variable or array index that doesn't exist, it would give false. In your particular case you can use isset($verify_auth[0]), which will give you true when there is something in the array returned by the $stmt->fetchAll().

edited Oct 24, 2019 at 19:41

answered Oct 24, 2019 at 17:22

Andrey Kostenko

3821 silver badge8 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

another_stack_user999 Over a year ago

This does not work with the correct credentials, the array is always empty.

Andrey Kostenko Over a year ago

I think the code is correct, probably you pass POST parameters in the form with different names than the ones that are used here, or the credentials are wrong, or you connect to the different database? I don't know really. Try to echo POST values or manually execute your SQL to make sure it returns correct data outside of this code.

another_stack_user999 Over a year ago

thanks for help, turns out I had a permissions issue with new table in database.

deceze Over a year ago

Don’t use !empty when you just mean if ($verify_auth). See kunststube.net/isset.

Andrey Kostenko Over a year ago

Thank you, @deceze, it's a very helpful and interesting article. I'll edit the answer accordingly.

Collectives™ on Stack Overflow

PHP PDO query not returning any data, isset() showing data is returned

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related