I need Help with Form Validation

[Woad.php]

I'm trying to create a members system and i'm having problems with the form validation. I want to have the validation code in a seperate file and be able to check if the username (one of the form's fields) has been taken by querying the database and comparing names. How do I do this?

[jwk811]

to see if the username is taken you will need to select that name from the row and find out how many rows had that information.. if it returns 0 then its not taken if more than 0 it is taken.. heres an example..
[code]$sql_username_check = mysql_query("SELECT username FROM users 
    WHERE username='$username'");
$username_check = mysql_num_rows($sql_username_check);
    if($username_check > 0){
echo "Username is already being Used! Please submit another email address!";
    } [/code]

[Woad.php]

OK, thanks that's better than what I was thinking of doing to check the username. But that still doesn't answer my validation issues.

[jwk811]

i dont understand what your trying to do.. can you explain it better?

[Woad.php]

I have a form on my webpage. Let's say I have three fields. Username, Email, and password. For all fields I have to check if they're too short or have invalid characters. For Username I need to check if it's been taken by another user, and for email I need to check whether it's a valid email. How do I perform these checks?

[jwk811]

for the length you can do this:
[code]    if(strlen($username) > 12 || strlen($username) < 4 ){
echo "Username should have 4 - 12 characters only";
if(strlen($username) > 12 ){
    echo "username is too long";
}
if(strlen($username) < 4 ){
    echo "username is too short";
}[/code]
and heres an email thing i already have written up
[code]if ($email_address) {
    if (!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $email_address)) {
        echo "The email you entered is not valid. Please try again. <br/>";
exit();
    }
} [/code]

[Woad.php]

But I do I validate the forms using that code?