php - 根据数据库 pdo 检查用户名

Question

该脚本可以将用户数据添加到数据库中，但是我想检查用户名是否正在使用，但一直遇到此错误

Fatal error: Call to a member function rowcount() on a non-object in /home/4507408/public_html/registeruser.php on line 78

我似乎无法使用 PDO 做到这一点，任何帮助都会很棒!

<?php
                $form = $_POST;
                $username = $form[ 'username' ];
                $password = $form[ 'password' ];
                $firstname = $form[ 'firstname' ];
                $location = $form[ 'location' ];
                $age = $form[ 'age' ];
                $email = $form[ 'email' ];

                $usercheck = $_POST['username'];

                 $check = "SELECT username FROM use WHERE username = '$usercheck'";
                 $query = $DBH->prepare( $check );
                 $query = $DBH->prepare($check);
                 $query->execute();
                 $data = $query->fetchALL();

                 $check2 = $check->rowcount();



                 //if the name exists it gives an error

                 if ($check2 != 0) {

                        die('Sorry, the username '.$_POST['username'].' is already in use.');

                                }

                $sql = "INSERT INTO user ( username, password, firstname, location, age, email ) VALUES ( :username, :password, :firstname, :location, :age, :email )";

                $query = $DBH->prepare( $sql );

                ?>

Answer 1

这一行:

$check = "SELECT username FROM use WHERE username = '$usercheck'";

错了。 use 是 SQL 保留字。我假设您指的是 user。使用简单的变量替换将值注入(inject)查询字符串也是一个糟糕的想法。 PDO 的重点是使用参数化查询:http://us1.php.net/pdo.prepared-statements