如果函数没有返回true，如何正确返回并显示字符串值？

问题描述：

I am attempting to write a method that checks whether a user exists and also does some validation.

This is the code so far:

public function checkUsername(){
            if((strlen($_POST['register-username']) > 2) && (strlen($_POST['register-username']) < 16)){
                $stmt = $this->dbh->prepare("SELECT username FROM adrenaline_junkies_uk_users WHERE username = ?");
                $stmt->bindParam(1, $this->post_data['register_username'], PDO::PARAM_STR);
                $stmt->execute();
                if($stmt->rowCount() != 0){
                        return TRUE;
                }else{
                    return $this->error .= '<span style="color:red;">Username already exists.</span>';
                }
            }else{
                return $this->error .= '<span style="color:red;">Username must be between 3 and 15 characters.</span>';
            }

    }

This is how Im attempting to call it:

if( isset($_POST['register-submit'])){

        $error = '';
        $register = new register($_POST, $dbh);
            if(!$error .= $register->checkUsername()){

                    //continue

            }else{
                $error .= $register->checkUsername();
            }
    }

To test it I don't enter anything in the input field to get the first error to be returned and echo it out correctly on the webpage. But nothing is displaying.

Is this the correct way of doing this? Sorry I'm not very familiar with using methods in classes. I assume I'm doing something wrong in the initial if statement in the calling program and should I be running that method twice like I do?

答

Use Exceptions. Like:

public function checkUsername(){
    if((strlen($_POST['register-username']) > 2) && (strlen($_POST['register-username']) < 16)){
        $stmt = $this->dbh->prepare("SELECT username FROM adrenaline_junkies_uk_users WHERE username = ?");
        $stmt->bindParam(1, $this->post_data['register_username'], PDO::PARAM_STR);
        $stmt->execute();
        if($stmt->rowCount() != 0){
                return TRUE;
        }else{
            throw new Exception("Username already exists.");
        }
    }else{
        throw new Exception("Username must be between 3 and 15 characters.");
    }

}

and

if( isset($_POST['register-submit'])){

    $error = '';
    $register = new register($_POST, $dbh);
    try {
        if($register->checkUsername()){
            //continue
        }
    } catch ($e) {
        $error .= '<span style="color:red;">' . $e->getMessage() . '</span>';
    }
}

You can do subclassing like:

class UsernameException extends Exception {}

try {
    throw new UsernameException("Your username is too awesome");
} catch (UsernameException $e) {
    exit($e->getMessage());
} catch (SomeOtherException $e) {
    exit("500");
} catch (Exception $e) {
    exit("que?");
}

如果函数没有返回true，如何正确返回并显示字符串值？

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