Assuming you have odbc driver , and dsn registered on your webserver, this is how you do it.
<?php
$db='your databse name';
$usrname='username';
$pwd='your password';
$conn = odbc_connect($db,$usrname,$pwd);
?>
Now let us assume you want to update your database with something that user inputs in your text box, lets say his Display name on your website, and password.
Lets assume textbox for name is txtname and for password (type="password" for asterics) is txtpass.
When user clicks on submit (name btnsubmit), lets say this info should be updated in a table called User in your database $db. Also assume form method is post and action is on same page (example newuser.php)
<?php
if(isset($_REQUEST['btnsumbit']))
{
$query="insert into table User values('".$_REQUEST['txtname']."','".$_REQUEST['txtpass']."')";
odbc_exec($conn,$query);
?>
}
Ofcourse this code dont handle any errors/exceptions and if u want to fetch data from database. u can use method
$recordset=odbc_exec($conn,$query);
odbc_fetch_row($recordset);
where query could be something like select * from User.
Good Luck!