How to Avoid the \'Trying to access array offset on value of type bool\' Error in PHP Database Queries?

How to Handle "Trying to access array offset on value of type bool" Error When Checking for Database Existence

When attempting to check for the existence of a record in a database, developers may encounter the "Trying to access array offset on value of type bool" error. This typically occurs when the database query returns no results, resulting in a boolean value of false being returned.

Addressing this error requires verifying whether any records were retrieved from the database. This can be achieved by encapsulating the database fetch operation within a conditional statement that checks for its existence.

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

Alternatively, you can assign a default value if the database returned nothing.

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

To correctly check for database existence using PDO, it's recommended to use the following approach:

$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!");
}

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

This method fetches the count of matching rows and evaluates it as a boolean, eliminating the need for further comparison in PHP.

To check for the existence of either the username or email in a single query, the following can be used:

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

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