当用户注册网站时，用户名中有空格、句点或@时，似乎会产生问题。如何包含这些字符？
MySQL非常关心用户名或密码中的字符，除非您没有正确构建查询：
$password = $_POST['password'];
$username = $_POST['username'];
$quoted_pass = mysql_real_escape_string($password);
$quoted_user = mysql_real_escape_string($username);
$sql = "INSERT INTO users (username, password) VALUES ('$quoted_pass', '$quoted_user');
$result = mysql_query($sql) or die(mysql_error());
if (mysql_affected_rows($result) != 1) {
die("User record not created");
}