我正在尝试创建一个帐户注册页面,当我添加一个系统来检查数据库并确保没有多个具有相同用户名的行时,出现500错误.

这是有效的代码：

if(isset ($_POST['submit']))

{

include( 'connection.php' );

$username = $_POST['username'];

$password = $_POST['password'];

$email = $_POST['email'];

if(empty($username) || empty($email) || empty($password))

{

echo 'Please check the required fields.';

}

elseif(!filter_var($email,FILTER_VALIDATE_EMAIL))

{

echo 'Please enter a correct email address.';

}

else

{

$password = md5($password);

$sql = mysql_query("INSERT INTO users (email,username,password) VALUES ('$email','$username','$password')") or die(mysql_error());

if($sql)

{

echo 'Successfully submitted.';

}

}

}

?>

这是给我500错误的代码：

error_reporting(E_ALL)

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

include( 'connection.php' );

$username = $_POST['username'];

$password = $_POST['password'];

$email = $_POST['email'];

$fetch = mysql_query("SELECT * FROM users WHERE username = '$email'") or die(mysql_error();

$num_rows = mysql_num_rows($fetch);

if(empty($username) || empty($email) || empty($password)) {

echo 'Please check the required fields.';

}

elseif(!filter_var($email,FILTER_VALIDATE_EMAIL)) {

echo 'Please enter a correct email address.';

}

elseif($num_rows >= 1);

{

echo 'This username is taken.';

else

}

$password = md5($password);

$sql = mysql_query("INSERT INTO users (email,username,password) VALUES ('$email','$username','$password')") or die(mysql_error());

if($sql)

{

echo 'Successfully submitted.';

}

}

}

?>