isset submit is not working
<p>I am using <code>isset</code> function to check if the submit button is clicked, but it's not working. It is not entering into the <code>if</code>. here is my code. I am not getting where the problem persists. </p>

<pre><code>&lt;table width="100%" border="0" cellspacing="0" cellpadding="0"&gt;
    &lt;tr&gt;
        &lt;td&gt;&lt;h2&gt;&lt;br /&gt;
            User Registration&lt;/h2&gt;
            &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
        &lt;td&gt;
            &lt;form action="&lt;?php echo $_SERVER['PHP_SELF']; ?&gt;" method="post" name="form1" id="form1" onsubmit="return Validate();"&gt;
                User Name[E-mail ID]: &lt;input type="text" name="username" style="width:230px; height:20px;" /&gt;&lt;br /&gt;&lt;br /&gt;
                Password : &lt;input type="password" name="password" style="width:230px; height:20px;" /&gt;&lt;br /&gt;&lt;br /&gt;
                Name &lt;input type="text" name="name" style="width:230px; height:20px;" /&gt;&lt;br /&gt;&lt;br /&gt;
                Contact Number: &lt;input type="text" name="phone" style="width:230px; height:20px;" /&gt;&lt;br /&gt;&lt;br /&gt;
                Email: &lt;input type="text" name="email" style="width:230px; height:20px;" /&gt;&lt;br /&gt;&lt;br /&gt;
                &lt;input type="submit" value="REGISTER" /&gt;
            &lt;/form&gt;

            &lt;?php
            include('connect.php');
            if (isset($_POST['submit']))
            {
                echo "1";
                $username = $_POST['username'];
                echo $username;

                $password = $_POST['password'];
                $name = $_POST['name'];
                $phone = $_POST['phone'];   

                $email = $_POST['email'];
                //$id = $_GET['aid'];

                $sql = "INSERT INTO user_info(application_id, username, password, name, contact, email) VALUES (" . $aid. ", " .$username.", ".$password.", ".$name.",". $phone.", ".$email.") ";
                echo $sql;
                mysql_query($sql) or die(mysql_error());
                //header("Location: index1.php");
            }

            ?&gt;

        &lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
        &lt;td&gt;&amp;nbsp;&lt;/td&gt;
    &lt;/tr&gt;
&lt;/table&gt;
</code></pre>

<p>Please let me know where I am going wrong.</p>
