isset提交无效

Question

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

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

            <?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");
            }

            ?>

        </td>
    </tr>
    <tr>
        <td>&nbsp;</td>
    </tr>
</table>

Please let me know where I am going wrong.

Answer 1

Change

<input type="submit" value="REGISTER" />

to

<input type="submit" name="submit" value="REGISTER" />