检查数据库jquery + php中是否已经存在电子邮件

Question

Hy I'm trying to validate the email address in a registration form. I want to check if the address exists in the database;

i have the following function:

function validateEmailRepeat(){
        // check if email exists in the database;
             var emailVal = $('#email').val();
             // assuming this is a input text field

            $.post('check_email.php', {'email' : emailVal}, function(data) {
                    if(data==1) 
                        {
                        email.addClass("error");
                        emailInfo.text("Adress exists");
                        emailInfo.addClass("error");
                        dataExist=1;
                            }

                    else {

                        email.removeClass("error");
                        emailInfo.text("Valid adress");
                        emailInfo.removeClass("error");
                        dataExist=0;
                            }
                        });

                        if(dataExist==1)
                         return false;
                         else
                         return true;

                    }

the check_email.php looks like this:

require_once('db.php');

if (isset($_POST['email'])){
$email=mysqli_real_escape_string($con,$_POST['email']);
$sql = "SELECT * FROM users WHERE `username`='".$email."'";
$select=mysqli_query($con,$sql) or die("fail");
$row = mysqli_num_rows($select);

if ($row >0) {

    echo 1;
}else echo 0 ;

}
else
echo "post error";

i'm new at this . So don't be to tough. thanks in advance.

LE:Sorry ! i forgot the question... the problem is that my function returns true if I define var dataExist outside of the function form $.post and if i let it like it is now in the function I get "dataExist is not defined " error and returns true

Le: the PHP returns the expected 1 and 0 just the way i wanted..

LE: seems like defining the

var dataExist=0;

outside the function validateEmailRepeat() resolved the issue.

if there's another way more elegant please tell me because this seems a little stupid to me.

Answer 1

The problem is you cannot return the value into the called function, because ajax work asynchronously.

                function validateEmailRepeat(){
                // check if email exists in the database;
                     var emailVal = $('#email').val();
                // assuming this is a input text field

                $.post('check_email.php', {'email' : emailVal}, function(data) {
                    if(data==1){
                        email.addClass("error");
                        emailInfo.text("Adress exists");
                        emailInfo.addClass("error");
                        dataExist=1;
                    }else{
                        email.removeClass("error");
                        emailInfo.text("Valid adress");
                        emailInfo.removeClass("error");
                        dataExist=0;
                    }
                        $('#some_input').val(dataExist);
                        validateUserName();
                    });
                }

                function validateUserName() {
                    var input =  $('#some_input').val();
                    if (input) {
                       alert("This username is already taken");// whatever
                    } else {
                         // whatever
                    }

                };

Answer 2

You are comparing the username with the email address. Is this how your DB works?

$sql = "SELECT * FROM users WHERE username ='".$email."'";

I bet you have a field in your database for the email itself, otherwise i suggest you do this. The query should look like this:

$sql = "SELECT * FROM users WHERE email = '".$email."'";

Without the single quotes for the column.