php - 如何检查电子邮件地址是否存在。验证

Question

我似乎不知道如何检查我的数据库中是否存在电子邮件。目前，用户使用他们的电子邮件地址使用密码登录我的网站，但目前用户可以使用同一电子邮件地址注册多次，这会导致我的网站出现大问题。已经做了一些研究，但似乎无法解决。

谁能帮帮我？

<?php       

if(isset($_POST['add']))
{
$dbhost = 'localhost';
$dbuser = 'user';
$dbpass = 'pass';
$db = "db";
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
  die('Could not send your enquiry at this time please try again later.');
}


$phone = mysql_real_escape_string((string)$_POST['phone']);
$email = mysql_real_escape_string((string)$_POST['email']);
$password = mysql_real_escape_string((string)$_POST['password']);
$firstname = mysql_real_escape_string((string)$_POST['firstname']);
$surname = mysql_real_escape_string((string)$_POST['surname']);
$country = mysql_real_escape_string((string)$_POST['country']);
$nationality = mysql_real_escape_string((string)$_POST['nationality']);
$yearofbirth = mysql_real_escape_string((string)$_POST['yearofbirth']);  
$profession = mysql_real_escape_string((string)$_POST['profession']); 
$status = mysql_real_escape_string((string)$_POST['status']); 
$membertype = 'Registered';
$dateregistered = mysql_real_escape_string((string)$_POST['dateregistered']); 
$agreedtoterms = mysql_real_escape_string((string)$_POST['agreedtoterms']); 

$sql = "INSERT INTO members
       (phone, email, password, firstname, surname, country, nationality, yearofbirth, profession, uniquepin, status, membertype, dateregistered, agreedtoterms)
       VALUES('$phone', '$email', '$password', '$firstname','$surname','$country','$nationality','$yearofbirth','$profession','$uniquepin','$status','$membertype','$dateregistered', '$agreedtoterms')";


mysql_select_db($db);
$retval = mysql_query( $sql, $conn )or die(mysql_error());

?>

Answer 1

您可以使 email 列具有唯一约束 - 然后在尝试插入时查询将失败。

你也可以直接查询....

SELECT `email`
  FROM `members`
 WHERE `email` = '$email'
 LIMIT 1

如果您得到结果，则该电子邮件存在。