How can PHP be used to query a database for existing nicknames before inserting new registration data?

To query a database for existing nicknames before inserting new registration data, you can use a SELECT query to check if the nickname already exists in the database. If the query returns any results, it means the nickname is already taken and the registration should be rejected. 

// Connect to the database
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// Query to check if nickname already exists
$nickname = $_POST['nickname'];
$sql = "SELECT * FROM users WHERE nickname = '$nickname'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    echo "Nickname already taken. Please choose a different one.";
} else {
    // Proceed with inserting new registration data
    // Insert query goes here
}

// Close the connection
$conn->close();

Keywords

PHP database query registration data nicknames error handling

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