Javascript，Php，Ajax

I have a problem with this my script.

$("#login").click(function(event) {

    event.preventDefault();

    var email = $("#email").val();
    var pass = $("#password").val();

    $.ajax({

        url : "login.php",
        method: "POST",
        data: {userLogin:1, userEmail:email, userPassword:pass},
        success : function(data){

            if(data == "1"){

                alert(data);
            }

        }

    })

I want it to alert a value that I am getting from an echo in another php file

<?php

    if(isset($_POST['userLogin'])){

        $email = mysqli_real_escape_string($con, $_POST['userEmail']);

        $password = md5($_POST['userPassword']);

        $sql_login = "SELECT * from database where email = '$email' AND password = '$password'";

        $query_login = mysqli_query($con, $sql_login);

        $count_login = mysqli_num_rows($query_login);

        if($count_login == 1){

            $row_login = mysqli_fetch_assoc($query_login);

            $_SESSION['uid'] = $row_login['user_id'];

            $_SESSION['name'] = $row_login['first_name'];

            echo "1";

        }


    }

    ?>

If I didn't put the alert(data) in an if condition, it displays the value I echo, but I need the condition to enable the right user logged in.

What can IF can also ELSE.

In your ajax add the else conditions to see if it helps uncover the issue:

if (data == "1") {
  alert('youre in');
} else {
  alert('try again');
}

And in your php, also account for the else condition (and do strict checking on that count of rows with ===):

if ($count_login === 1) {
  // code ...
  echo '1';
} else {
  echo 'Sorry, the login is incorrect';
}

It works fine for me, if i always echo "1", the alert(data) show 1, in an if condition and out, pls, echo something else if isset($_POST['userLogin']) or $count_login == 1 are false, or put an

error : function(data) {
    $('body').append("<div>"+data.responseText+"</div>")
}

in your ajax, to debug the prob. Because in your .php file, when you echo nothing, it returns a data in error, not in success, maybe that's your prob.