Why am I getting the \'Trying to Access Array Offset on Value of Type Bool\' error when checking database query results?

Error: "Trying to Access Array Offset on Value of Type Bool"

In this code snippet, you're attempting to access the Username and Email keys in the $nameRes and $emailRes arrays to check if they match the user inputs. However, you're getting the error "Trying to access array offset on value of type bool."

Cause

This error occurs when the database query returns a Boolean value, typically true or false, indicating whether there's a match in the database. If there's no match, the query would return false. In your case, when the database doesn't find a matching Username or Email, it returns false, making the $nameRes or $emailRes array a Boolean value.

Solution

There are several ways to handle this situation:

1. Check for Null or Empty Results

Before accessing the Username or Email keys, check if the arrays are null or empty:

if ($nameRes && !empty($nameRes['Username']) {
    // Proceed with username check
}

2. Use Default Values

If you don't care whether the record exists in the database, assign a default value to the keys:

$name = $nameRes['Username'] ?? '';
$email = $emailRes['Email'] ?? '';

if ($name == $_POST['username']) {
    // Proceed with username check
}

3. Use PDO's FetchColumn

Instead of fetching the entire row and comparing it in PHP, use fetchColumn() to fetch only the count of matching rows. This returns a single value (either 0 or a non-zero integer), which you can use in an if statement:

$query = $pdo->prepare("SELECT COUNT(*) FROM Users WHERE Username = :Username");
$query->execute([':Username' => $name]);
if ($query->fetchColumn()) {
    // Proceed with username check
}

4. Use a Single Query

You can combine the username and email checks into a single query by using an OR condition:

$query = $pdo->prepare("SELECT COUNT(*) FROM Users WHERE Username = :Username OR Email = :Email");
$query->execute([':Username' => $name, ':Email' => $email]);
if ($query->fetchColumn()) {
    // Proceed with username/email check
}

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