onblur文本框生成电子邮件已存在于数据库中的警报

我有一个PHP函数，它响应的数据是唯一的，不是，我想用JavaScript调用它。如果电子邮件已经存在，则停止到表单提交，否则可以提交表单。

    <?php include'class.php'; ?>
    Enter your email: <input type="text" id="email" onblur="myFunction()">
     <script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
     <script type="text/javascript">
       function myFunction() { $(document).ready(function() {
            var x = document.getElementById("email").value;
    if(y=0){
            alert('already exist');}
        });}
        </script>
it is presented in a php class file
public function unique($table,$col,$comp){include'db.php';
            $query="SELECT count(*) as flag FROM $table where $col='$comp'";            
            $result = mysqli_query($con,$query);
            while($row = mysqli_fetch_array($result)){$flag=$row['flag'];}
            if($flag==0){return 0;}else{return 1;}}