准备好的SQL语句INSERT

Question

I am currently following W3Schools tutorial with Prepared SQL statements, When I try to insert data into the database it's saying $firstname = "Nathan" and $lastname = "Kent" is an unused local variable? Also it returns no error so it's connecting fine and when I check the database it has no new entries.

 function setData(){
    global $servername;
    global $username;
    global $password;
    global $dbname;

    $conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
     if ($conn->connect_error) {
         die("Connection failed: " . $conn->connect_error);
     } else{
         echo "Connection Successful" . "<br>";
   }
    $stmt = $conn->prepare("INSERT INTO test(firstname, surname) VALUES       (?,?)");
    $stmt->bind_param("ss", $firstname, $surname);

    $firstname = "James";
    $lastname = "Williams";
    $stmt->execute();

    echo "New Records Created";

    $stmt->close();
    $conn->close();

}

Answer 1

With MYSQLI you actually need to look for errors rather than assuming they will shout at you.

function setData(){
    global $servername;
    global $username;
    global $password;
    global $dbname;

    $conn = new mysqli($servername, $username, $password, $dbname);

    // Check connection
    if ($conn->connect_error) {
         die("Connection failed: " . $conn->connect_error);
    } else{
         echo "Connection Successful" . "<br>";
    }
    $stmt = $conn->prepare("INSERT INTO test(firstname, surname) VALUES (?,?)");

    // add error check
    if ( $stmt === false ) {
        echo $conn->error;
        exit;
    }

    // Its not necessary to load the variables before the `bind_param`
    // but as you dont actually have these variables yet you do
    $firstname = "James";
    $lastname = "Williams";

    $stmt->bind_param("ss", $firstname, $surname);

    $status = $stmt->execute();

    // add error check
    if ( $status === false ) {
        echo $conn->error;
        exit;
    }


    echo "New Records Created";

    $stmt->close();
    $conn->close();

}

You could clean this up a bit as well by connecting to the database in the mainline code and passing the connection param to the function as well as the data parameters

function setData($conn, $firstname, $lastname){

    $stmt = $conn->prepare("INSERT INTO test(firstname, surname) VALUES (?,?)");

    // add error check
    if ( $stmt === false ) {
        echo $conn->error;
        exit;
    }

    $stmt->bind_param("ss", $firstname, $surname);

    $status = $stmt->execute();

    // add error check
    if ( $status === false ) {
        echo $conn->error;
        exit;
    }

    return "New Records Created";

    $stmt->close();
    $conn->close();

}


$servername = '127.0.0.1';
$username   = 'root';
$password   = 'veryStRongPassPhrASe';
$dbname     = 'mydatabase';

$conn = new mysqli($servername, $username, $password, $dbname);

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


$msg = setData($conn, 'Fred', 'Bloggs');
echo $msg;