普莱斯试试这个

mysqli_query("SELECT * FROM Register WHERE email = '$email' and password ='$password'"); 

if(mysql_num_rows($query)) 
{ 
      echo ' 
      <script> 
      alert("Succesful Login"); 
      window.history.go(-1); 
      </script>'; 
      exit; 
} 
else 
{ 
      echo ' 
      <script> 
      alert("The email is not the same or does not exist"); 
      window.history.go(-1); 
      </script>'; 
      exit; 

} 

更改查询像下面

SELECT password FROM Register WHERE email = '$email' AND password = '$password'

还可以使用mysqli的*因为MySQL *已弃用并已彻底删除，在7页

https://www.w3schools.com/php/php_ref_mysqli.asp

您使用
1. “” 而不是 “AND”。使用和它应该解决

2. 执行第二个查询后，您的数据将在$查询。你必须使用

   $data=mysql_fetch_array($query); 
   $data['password'];// there contains password 
   so you code this 
   if($query2==$password) 
        { 
         echo ' 
         <script> 
         alert("Succesful Login"); 
         window.history.go(-1); 
         </script>'; 
         exit; 
        } 
   will be changed to 
   if($data['password']==$password) 
        { 
         echo ' 
         <script> 
         alert("Succesful Login"); 
         window.history.go(-1); 
         </script>'; 
         exit; 
        } 
   

希望得到您的答复。