The result of php code is wrong? : When i tried to code a simple php code, i had a problem that the result had showed some things which weren't expected such as "***' . "\n"; echo'*** ". Where is my code wrong?
Here is my code:

    <html>
    <head>
    <title>Putting Data in the DB</title>
    </head>
    <body>
    <?php
    /*insert students into DB*/
    if(isset($_POST["submit"])) {
    $db = mysql_connect("mysql", "martin");
    mysql_select_db("martin");
    $date=date("Y-m-d");  /* Get the current date in the right SQL format */
    $sql="INSERT INTO students  VALUES(NULL,'" . $_POST["f_name"] . "','" . 
    $_POST["l_name"] . "'," . $_POST["student_id"] . ",'" . $_POST["email"] . 
    "','" . $date . "'," . $_POST["gr"] . ")";  /* construct the query */
    mysql_query($sql);  /* execute the query */ 
    mysql_close();
    echo"<h3>Thank you. The data has been entered.</h3> \n";
    echo'<p><a href="data_in.php">Back to registration</a></p>' . "\n";
    echo'<p><a href="data_out.php">View the student lists</a></p>' ."\n";
    }
    <html>
    <head>
    <title>Putting Data in the DB</title>
    </head>
    <body>
    <?php
    /*insert students into DB*/
    if(isset($_POST["submit"])) {
    $db = mysql_connect("mysql", "martin");
    mysql_select_db("martin");
    $date=date("Y-m-d");  /* Get the current date in the right SQL format */
    $sql="INSERT INTO students  VALUES(NULL,'" . $_POST["f_name"] . "','" . 
    $_POST["l_name"] . "'," . $_POST["student_id"] . ",'" . $_POST["email"] . 
    "','" . $date . "'," . $_POST["gr"] . ")";  /* construct the query */
    mysql_query($sql);  /* execute the query */ 
    mysql_close();
    echo"<h3>Thank you. The data has been entered.</h3> \n";
    echo'<p><a href="data_in.php">Back to registration</a></p>' . "\n";
    echo'<p><a href="data_out.php">View the student lists</a></p>' ."\n";
    }

Result is here:

> Thank you. The data has been entered. \n"; echo' Back to registration
> 
> ' . "\n"; echo' View the student lists
> 
> ' ."\n"; } Thank you. The data has been entered. \n"; echo' Back to
> registration
> 
> ' . "\n"; echo' View the student lists
> 
> ' ."\n"; }