Question

我尝试以注册表格验证用户名字段，并检查所选用户名是否已存在于数据库中，但无法按预期工作。我不知道如何解决这个问题。这是来源

$query = "SELECT * FROM users WHERE username = :username";
$sq = $pdo->prepare($query);
$sq->execute(array(
         ':username'    => $username                                
        ));
$res=$sq->fetch();
if (!$res) {
    echo ' Database Error Occured ';
}
else { echo "username already exist in database"; }

if ($res === 0) {
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $pdo->beginTransaction();
    try 
    {
         $sql = "INSERT INTO users ( username, password, email, path)
                            VALUES (:username, :password, :email, :path)";

                $q = $pdo->prepare($sql);
                $q->execute(array(
                    ':username' => $username,
                    ':password' => $password,
                    ':email'    => $email,
                    ':path'     => $path                                
                    ));                 

                $lastInsertID = $pdo->lastInsertId();
                $sql = $pdo->prepare("UPDATE users SET level=:user_id WHERE user_id=:user_id");
                $sql->execute(array(
                    ':user_id'  => $lastInsertID
                    ));
                $pdo->commit();     
     }

当我点击提交按钮时发生的事情如果我输入了存在的用户名username already exist in database但是如果我输入另一个不存在的用户名{} {}}

Answer 1

if(1 < $res->rowCount()){
    print('username already exist');
}

Answer 2

你必须替换这个

 if (!$res) {
        echo ' Database Error Occured ';
    }
    else { echo "username already exist in database"; }
if ($res === 0) {

由此

if ($res) {
    echo "username already exist in database";
}else{

Answer 3

因为$sq->fetch()返回FALSE（它不存在）。您应该将支票更改为：

if ($res) {
    echo "username already exist in database";
}

和

if ($res === FALSE) {
// Username does not exist
}

检查数据库中是否已存在用户名

3 个答案: