What is the best practice for checking if a record already exists before adding a new entry in PHP without using the primary key as a criterion?

When checking if a record already exists before adding a new entry in PHP without using the primary key as a criterion, you can use a unique field in the database table to verify if the record already exists. One common approach is to check against a unique column like an email address or username. You can query the database to see if any records already exist with the same value in the unique field before attempting to insert a new entry.

// Assuming $conn is your database connection

// Check if a record already exists with the given email address
$email = "example@example.com";
$sql = "SELECT * FROM your_table_name WHERE email = :email";
$stmt = $conn->prepare($sql);
$stmt->bindParam(':email', $email);
$stmt->execute();
$count = $stmt->rowCount();

if ($count > 0) {
    echo "Record already exists with this email address.";
} else {
    // Proceed with inserting the new entry
}