Why Am I Getting a \'Trying to access array offset on value of type bool\' Error in My PHP Code?

Unable to Access Array Offset on Boolean Value in PHP

Encountering the error "Trying to access array offset on value of type bool" in PHP signifies that the code attempts to retrieve an array element from a value that's not an array, in this case, a boolean.

In the provided code, you are querying the database for users based on their username and email. Upon receiving a result, you check if the username or email already exists by comparing the database response with the input from the registration form.

However, the error occurs when the database query returns no records matching the criteria. As a result, $emailRes (and $nameRes) becomes a boolean (false) instead of an associative array. Consequently, accessing $emailRes['Email'] throws the error since you cannot access an array offset on a boolean value.

Resolving the Issue

Check for Database Results:

The easiest solution is to first check if the database query returns any results before attempting to access the $emailRes array.

$emailRes = $query->fetch(PDO::FETCH_ASSOC);
if ($emailRes) {
    // Proceed to use $emailRes
}

Provide a Default Value:

If you don't care whether the database returned anything, you can provide a default value.

$emailRes = $query->fetch(PDO::FETCH_ASSOC);
$email = $emailRes['Email'] ?? ''; // Default: empty string

Alternative Approach:

A better practice is to use PDO's rowCount() or fetchColumn() methods to check for the existence of rows in the database, avoiding the potential boolean result.

$query = $pdo->prepare("SELECT COUNT(*) FROM Users WHERE Username = :Username");
$query->execute([':Username' => $name]);
if ($query->fetchColumn()) {
    throw new \Exception("Username is already in use!");
}

By checking the row count instead of fetching the data, you eliminate the possibility of receiving a boolean result, ensuring that you won't encounter the "array offset on boolean" error.

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