检查我的数据库中是否存在用户名和电子邮件

Question

我是PHP新手，我想检查一下用户名或电子邮件是否已经存在于我的数据库中。如果是这样，我想重定向到我的注册页面。代码我有工作添加用户，但我无法弄清楚如何检查用户名和电子邮件是否存在。我不想做任何主键请帮忙!!!这是我现在已经从我使用这本书的代码：

<?php 
require_once "app_config.php"; 
require_once "database_connection.php"; 

$upload_dir = HOST_WWW_ROOT . "uploads/profile_pics/"; 
$image_fieldname = "user_pic"; 

//Potential PHP errors 
$php_errors = array(1 => 'Maximum file size in php.ini exceeded', 
        2 => 'Maximum file size in HTML form exceeded', 
        3 => 'Only part of the file was uploaded', 
        4 => 'No file was selected to upload'); 

$first_name = trim($_REQUEST['first_name']); 
$last_name = trim($_REQUEST['last_name']); 
$username = trim($_REQUEST['username']); 
$password = trim($_REQUEST['password']); 
$email = trim($_REQUEST['email']); 
$bio = trim($_REQUEST['bio']); 
$facebook_url = str_replace("facebook.org", "facebook.com", trim($_REQUEST['facebook_url'])); 
$position = strpos($facebook_url, "facebook.com"); 
if($position === false) { 
    $facebook_url = "http://www.facebook.com/" . $facebook_url; 
} 
$twitter_handle = trim($_REQUEST['twitter_handle']); 
$twitter_url = "http://www.twitter.com/"; 
$position = strpos($twitter_handle, "@"); 
if($position === false) { 
    $twitter_url = $twitter_url . $twitter_handle; 
} else { 
    $twitter_url = $twitter_url . substr($twitter_handle, $position + 1); 
} 

//Make sure we didn't have an error uploading the image 
($_FILES[$image_fieldname]['error'] == 0) 
    or handle_error("the server couldn't upload the image you selected", 
        $php_errors[$_FILES[$image_fieldname]['error']]); 

// Is this file the result of a valid upload? 
@is_uploaded_file($_FILES[$image_fieldname]['tmp_name']) 
    or handle_error("you were trying to do something naughty. Shame on you!", 
        "Uploaded request: file named " . 
        "'{$_FILES[$image_fieldname]['tmp_name']}'"); 

// Is this actually an image? 
@getimagesize($_FILES[$image_fieldname]['tmp_name']) 
    or handle_error("you selected a file for your picture " . 
        "that isn't an image.", 
        "{$_FILES[$image_fieldname]['tmp_name']} " . 
        "isn't a valid image file."); 

//Name the file uniquely 
$now = time(); 
while(file_exists($upload_filename = $upload_dir . $now . 
        '-' . $_FILES[$image_fieldname]['name'])) { 
    $now++; 
} 

// Insert the image into the images table 
$image = $_FILES[$image_fieldname]; 
$image_filename = $image['name']; 
$image_info = getimagesize($image['tmp_name']); 
$image_mime_type = $image_info['mime']; 
$image_size = $image['size']; 
$image_data = file_get_contents($image['tmp_name']); 

//Insert into images query 
$insert_image_sql = sprintf("INSERT INTO images " . 
         "(filename, mime_type, file_size, image_data) " . 
        "VALUES ('%s', '%s', %d, '%s');", 
         mysql_real_escape_string($image_filename), 
         mysql_real_escape_string($image_mime_type), 
         mysql_real_escape_string($image_size), 
         mysql_real_escape_string($image_data)); 

mysql_query($insert_image_sql) 
    or die(mysql_error()); 

//Insert into users query 
$insert_sql = sprintf("INSERT INTO users " . 
         "(first_name, last_name, username, " . 
         "password, email, " . 
         "bio, facebook_url, twitter_handle, " . 
         "profile_pic_id) " . 
      "VALUES ('%s', '%s', '%s', '%s', '%s', 
        '%s', '%s', '%s', %d);", 
         mysql_real_escape_string($first_name), 
         mysql_real_escape_string($last_name), 
         mysql_real_escape_string($username), 
         mysql_real_escape_string($password), 
         mysql_real_escape_string($email), 
         mysql_real_escape_string($bio), 
         mysql_real_escape_string($facebook_url), 
         mysql_real_escape_string($twitter_handle), 
         mysql_insert_id()); 

//Insert user into database 
mysql_query($insert_sql) 
    or die(mysql_error()); 

//Redirect the user the page that displays user information 
header("Location: show_user.php?user_id=" . mysql_insert_id()); 
exit(); 

>

Answer 1

首先一个伟大的小费。 PHP中的mysql函数已过时，您应该阅读有关PDO的一些信息。

但现在插入查询之前添加此。

if(mysql_num_rows(mysql_query("SELECT ID FROM users WHERE email = '". mysql_real_escape_string($email) ."')) != 0) { 
    exit("email exists"); 
} 

Answer 2

select count(1) from users where email = '[INSERT USERNAME TO CHECK HERE]' 

获得0回到意味着有与该用户名没有用户。

您还需要在插入之前将所有用户名小写，以防止'鲍勃'与'鲍勃'与'BOB'的情况。

Answer 3

最安全的方法是让数据库执行检查。这称为“唯一约束”，当它尝试添加重复项时，会导致任何更新或插入失败。

您可以轻松地只是通过创建唯一索引创建这个约束：

create unique index users_username on users(username); 
create unique index users_email on users(email);