两个查询和我得到一个完全空白的屏幕，错误报告显示什么

我看过一些关于这个问题的其他问题，但我相信我的问题是独一无二的。我正在处理一个表单，我相对较新的PHP和PDO，所以没有最好的调试技能。我相信我的查询是错误的，因为当我按下提交按钮时，它只是抛出一个空白页，没有错误消息(即使我有错误报告)。

我开始在mysql中写这个，但后来不得不废弃它，因为它不工作，我需要很容易地在我的插入语句中有变量。这是我的代码

error_reporting(-1);    
       require 'scripts/PasswordHash.php';
       $username = $name = $email = $password = $gender = $age = '';
       $query = FALSE;
       $dbh = new PDO('mysql:host=localhost;dbname=some_database;charset=utf8', 'some_user', 'some_password');
       if ($_SERVER['REQUEST_METHOD'] == 'POST') {
           //Logic
            if (empty($_POST['age'])) {
               $errors[] = 'Please enter your age';
           }
           if (empty($_POST['gender'])) {
               $errors[] = 'Please select your gender';
           }
           if ($_POST['password'] != $_POST['passwordRep']) {
               $errors[] = 'You did not repeat your password properly';
           }
           if (empty($_POST['password'])) {
               $errors[] = 'Please enter a password';
           }
           if (empty($_POST['email'])) {
               $errors[] = 'Please enter your email in this format : xxxxx@xxx.xxx or xxxxx@xxx.xx.xx';
           }
           if (empty($_POST['name'])) {
               $errors[] = 'Please enter your name';
           }
           if (check("username", $_POST['username']) == TRUE) {
               $errors[] = 'That username already exists';
           }
           if (check("email", $_POST['email']) == TRUE) {
               $errors[] = 'That username already exists';
           }
           if (empty($_POST['username'])) {
                $errors[] = 'Please enter a username';
           }
           if (empty($errors)) {
               $username = trim($_POST['username']);
               $name = trim($_POST['name']);
               $email = trim($_POST['email']);
               $password = PassHash::hash($_POST['password']);
               $gender = trim($_POST['gender']);
               $age = trim($_POST['age']);
               $date = date("Y-m-d H:i:s");
               $hash = md5( rand(0,1000) );
               insert();
           }
       }

       function insert() {
           try {
                //connect as appropriate as above
                $sql= "INSERT INTO users VALUES(:username, :password, :name, :email, :date, :age, :gender, :hash)"; 
                $stmt = $dbh->prepare($sql);
                $stmt->bindParam(':username', $username, PDO::PARAM_STR);
                $stmt->bindParam(':password', $password, PDO::PARAM_STR);
                $stmt->bindParam(':name', $name, PDO::PARAM_STR);
                $stmt->bindParam(':email', $email, PDO::PARAM_STR);
                $stmt->bindParam(':date', $date, PDO::PARAM_STR);
                $stmt->bindParam(':age', $age, PDO::PARAM_STR);
                $stmt->bindParam(':gender', $gender, PDO::PARAM_STR);
                $stmt->bindParam(':hash', $hash, PDO::PARAM_STR);
                $stmt->execute();
                $query = TRUE;
                require 'scripts/sendEmailVerify.php';
            } catch(PDOException $ex) {
                echo "An Error occured!"; //user friendly message
                echo ($ex->getMessage());
            }
       }
       function check($field, $input) {
           try {
                $sql= "SELECT :field FROM users WHERE :field = :input"; 
                $stmt = $dbh->prepare($sql);
                $stmt->bindParam(':field', $field, PDO::PARAM_STR);
                $stmt->bindParam(':input', $input, PDO::PARAM_STR); 
                $stmt->execute();
                $row_count = $stmt->rowCount();
                if ($row_count > 0) {
                    return TRUE;
                } else {
                    return FALSE;
                }
            } catch(PDOException $ex) {
                echo "An Error occured!"; //user friendly message
                echo ($ex->getMessage());
            }
       }

我认为这可能是我有查询的功能发生(虽然我不知道)。我已经通过PHP代码检查器(http://phpcodechecker.com/)运行此代码，它很好，所以我不认为这是我的语法!谢谢你,

尼克

编辑:由于有关调试的链接，我已经找到了错误!