Problem with syntax

[FuG5333]

I have a signup list. Everything works except I want to be able to only allow people to signup once. If not then display a messge saying so. Here's what I have so far:

[code]function addname1()
    {
    $first_name = $_SESSION['first_name'];
    $username = $_SESSION['username'];

    connect();
    if (mysql_query(SELECT * FROM calendar WHERE $username = $_SESSION['username'])) { echo "You're already signed up!; exit(); }
    $sql = "INSERT INTO calendar (first_name, username, caldate)
                        VALUES('$first_name', '$username', now())";
    $query = mysql_query($sql);
    if ( !$query )
        {
        echo "didn't work...";
        exit();
        }
    echo "$first_name added for day";

    }[/code]

I can signup but just want to limit the times you can signup to one time. Ideas?

[obsidian]

instead of just putting your query inside the if statement, you'll need to see if any rows are returned:

[code]
<?php
// change this:
if (mysql_query(SELECT * FROM calendar WHERE $username = $_SESSION['username'])) { echo "You're already signed up!; exit(); }

// to this:
$sql = mysql_query("SELECT * FROM calendar WHERE username = '$_SESSION[username]'");
if (mysql_num_rows($sql) > 0) {
  echo "You're already signed up!";
  exit();
}
?>
[/code]