PHP pdo插入查询不起作用

<?php
// DATABASE-HOSTNAME-OR-IPADDRESS-GOES-HERE
// MYSQL-DBNAME-GOES-HERE
class LoginHandler {
    public $dbHostname = 'localhost';
    public $dbDatabaseName = 'employee101';
    public $user = 'root';
    public $password = 'root';
    public function handleRequest($arg) {
        $username = '123';
        $password2 = '123';
        $fname = 'John';
        $lname = 'Doe';
        $age = '18';
        if ( ! $username ) {
            $this->fail();
            return;
        }
        try  {
            $dsn = "mysql:dbname={$this->dbDatabaseName};host={$this->dbHostname};port=8888";
            $pdo = new PDO($dsn, $this->user, $this->password);
            $sql="SELECT * FROM `employee_data` WHERE `username`='$username'";
            $stmt = $pdo->query($sql);
            if ( $stmt === false ) {
                echo "DB Critical Error";
                return;
            }
            elseif ( $stmt->rowCount() > 0 ) {
                echo "user already exists";
                return;
            }
            else {
                echo "User created";
                $sql = "INSERT INTO employee_data (name, sumame, age, username, password)
                VALUES ($fname, $lname, $age, $username, $password2)";
                $dsn = "mysql:dbname={$this->dbDatabaseName};host={$this->dbHostname};port=8888";

                $pdo = new PDO($dsn, $this->user, $this->password);
                $stmtz = $pdo->prepare($sql);

                $stmtz->bindParam($fname, $_POST[$fname], PDO::PARAM_STR);
                $stmtz->bindParam($lname, $_POST[$lname], PDO::PARAM_STR);
                $stmtz->bindParam($age, $_POST[$age], PDO::PARAM_STR);
                $stmtz->bindParam($username, $_POST[$username], PDO::PARAM_STR);
                $stmtz->bindParam($password2, $_POST[$password2], PDO::PARAM_STR);

                $resultzzx = $stmtz->execute();
                return;
            }
        }
        catch(PDOException $e) {
            $this->log('Connection failed: ' . $e->getMessage());
            echo "DB Critical Error";
        }
    }
    function log($msg) {
        file_put_contents("login.log", strftime('%Y-%m-%d %T ') . "$msg
", FILE_APPEND);
    }
}
$handler = new LoginHandler();
$handler->handleRequest($_POST);
?>

When attempting to use this script above, I get the echo that the user was created, but even when refreshing the table, the new entry doesn't show up.

Now, if i change the values line to be the following, it will work and show the new entry.

('John', 'Doe', '18', $username, $password2)";

What am i doing wrong? I need the first name, last name and age entries to not be concrete, as i will be obtaining them from a POST on my android device. The whole purpose of this script is to create the user and it's records if it doesn't already exist.

You have various mistakes.

1) You are not binding your parameters correctly. To bind them correctly, you place a :variablename in the position you want to include the variable. Usually the "variablename" should be the same as the one you are obtaining from the $_POST superglobal so that the code is cleaner and more readable.

2) You are not obtaining the values from the $_POST superglobal correctly. The key values you place inside are strings, and by placing an empty $fname variable, you are not going to obtain a correct result. It would only work if you had coding saying $fname = 'fname' somewhere up top hidden from us, however that code itself would be unadvised since it is unnecessary and only makes the source code larger.

$sql = "INSERT INTO employee_data (name, sumame, age, username, password)
VALUES (:fname, :lname, :age, :username, :password2)";

$dsn = "mysql:dbname={$this->dbDatabaseName};host=
{$this>dbHostname};port=8888";

$pdo = new PDO($dsn, $this->user, $this->password);

$stmtz = $pdo->prepare($sql);

$stmtz->bindParam(':fname', $_POST['fname']);
$stmtz->bindParam(':lname', $_POST['lname']);
$stmtz->bindParam(':age', $_POST['age']);
$stmtz->bindParam(':username', $_POST['username']);
$stmtz->bindParam(':password2', $_POST['password2']);

I hope that helps.

 $sql = "INSERT INTO employee_data (name, sumame, age, username, password) VALUES (:name, :sumame, :age, :username, :password)";
                $dsn = "mysql:dbname={$this->dbDatabaseName};host={$this->dbHostname};port=8888";

                $pdo = new PDO($dsn, $this->user, $this->password);
                $stmtz = $pdo->prepare($sql);
                $stmtz->bindParam(':name', $fname);
                $stmtz->bindParam(':sumame', $lname);
                $stmtz->bindParam(':age', $age);
                $stmtz->bindParam(':username', $username);
                $stmtz->bindParam(':password', $password2);
                $resultzzx = $stmtz->execute();
                return;

After reviewing the link Fred posted in the comment above, i've modified it to work fine, thanks.