mysql_fetch_array没有返回任何内容

Can someone please help with below query. The code mentioned below is not returning FirstName and LastName. Why?

Cheers, Akhil G

<?php 

        $username = mysql_real_escape_string($_GET['user']);
        $firstname ="" ;
        $lastname ="";
            if (ctype_alnum($username))
            {
                //check user exist

                $check = mysql_query("SELECT username, first_name, last_name FROM syn where username = '$username'");
                if (mysql_num_rows($check) === 1)
                {
                    $get = mysql_fetch_array($check);
                    $username = $get['username'];
                    $firstname = $get['first_name'];
                    $lastname = $get['last_name'];
                } else 
                echo "<h2> User Does Not Exist ! </h2>";
                exit();
            }   
?>

you are using the wrong fetch function

$get = mysql_fetch_array($check);

stored data in numbered positions in the array, so the returned data is stored in $get[0], $get[1] and $get[2].

you can see the contents by using print_r($get);

Instead use

$get = mysql_fetch_assoc($check);

this stores the data in the associated array you require.

try this..

<?php 

        $username = mysql_real_escape_string($_GET['user']);
        $firstname ="" ;
        $lastname ="";
            if (ctype_alnum($username))
            {
                //check user exist

                $check = mysql_query("SELECT username, first_name, last_name FROM syn where username = '$username'");
                if (!$check)
                {
                    $get = mysql_fetch_row($check);
                    $username = $get[0];
                    $firstname = $get[1];
                    $lastname = $get[2];
                } else 
                    echo "<h2> User Does Not Exist ! </h2>";
                exit();
            }   
?>

Thanks Guys .. but seems I am out of luck .. nothing seems working .. tried all the options suggested .. below is the modified version which again not printiing firstname lastname or username

<?php
include("./inc/header.inc.php");
?>

<?php

if (isset($_GET['user']))
  {
    $username = mysql_real_escape_string($_GET['user']);
    $firstname ="" ;
    $lastname ="";
        if (ctype_alnum($username))
        {
            //check user exist
            $check = mysql_query("SELECT username, first_name, last_name FROM syn where username = '$username'");
            if (mysql_num_rows($check) === 1)
            {
                $get = mysql_fetch_assoc($check);
                $username = $get['username'];
                $firstname = $get['first_name'];
                $lastname = $get['last_name'];
            } else 
            echo "<meta http-equiv =\"refresh\" content=\"0; url = http://localhost:8080/FirstTry/Tests/index.php\">";
            exit();
        }
}   
?>

<div class="postForm" > Post form will go in here .. </div>
<div class="postPosts" > Your Post will go in here ..</div>
<img src ="" height="250" width="200" alt ="<?php echo $firstname; ?>'s profile" title="<? echo $firstname; ?>'s profile"/>