下拉列表在DB中显示表格

I am working on the following code where the user chooses a table from a dropdown. On change, it displays the table but at the moment it is echoing some of the code to screen.

   <?php
    $dbh = "localhost";
    $dbn = "dbname";
    $dbu = "dbuser";
    $dbp = "dbpassword";

    $conn = mysql_connect($dbh,$dbu,$dbp) or die("Unable to connect do database.");
    mysql_select_db($dbn, $conn) or die("Unable to select database."); 

    $result = mysql_query("SHOW TABLES FROM $dbn") or die("Cannot list table names.");
    echo "
    <form name=\"table_browser\" action=\"".$PHP_SELF."\" method=\"GET\" >
        <select name=\"t\" onChange=\"javascript:submit();\">
            <option>Select a table</option>
    ";
    while ($row = mysql_fetch_row($result)){
        echo "        <option value=".$row[0].">".$row[0]."</option>
";
    }
    echo "    </select>
    </form>
";

    if (!isset($t)){
        die("Please select a table");
    }
    ?>

You need to use full php code here

<?php 
?>