PHP web service to insert data to mysql database and retreive

<?php

 mysql_connect("localhost","pfdsr","sdffsd") or die("database error");
 mysql_select_db("sfdfsds");
   
    if (!empty($_POST)) {
   
    $Name = mysql_real_escape_string($_REQUEST['username']);
    $Email = mysql_real_escape_string($_REQUEST['email']);
    $Address= mysql_real_escape_string($_REQUEST['password']);
   
    $result = mysql_query("SELECT email from student WHERE email = '$Email'");
        $no_of_rows = mysql_num_rows($result);
        if ($no_of_rows > 0) {
            // user existed
                  $response["success"] = 2;
                  $response["message"] = "Email already registered!";
                  die(json_encode($response));
        } else {
   
       try {
            $query2 = mysql_query("INSERT INTO student VALUES(null, '$Name', '$Email', '$Address')")or die(mysql_error());
            //$result2 = mysql_query($query2);
   
            $last_insert_id = mysql_insert_id();
        $result = mysql_query("SELECT name, email, address FROM student WHERE id = '$last_insert_id' ")or die(mysql_error());
        $json = array();
        $row = mysql_fetch_assoc($result);
        $json['student'][] = $row;
        //echo json_encode($json);
       
          $response["success"] = 1;
                  $response["message"] = "Login successful!";
                  die(json_encode($response));
             }
              catch (PDOException $ex) {
                    $response["success"] = 0;
                        $response["message"] = "Database Error1. Please Try Again!";
                        die(json_encode($response));
                    }
     }
    } else {
?>
    <h1>Register</h1>
    <form action="enterdata.php" method="post">
        Username:<br />
        <input type="text" name="username" value="" />
        <br /><br />
        Password:<br />
        <input type="password" name="password" value="" />
        <br /><br />
         Email:<br />
        <input type="text" name="email" value="" />
        <br /><br />
        <input type="submit" value="Register New User" />
    </form>
    <?php
}

?>