So, only thing you have to do is to select records from the database and put them in the forms ( value="..." ). After submit you update the database with the new values.
Example :
<?php
// connect to SQL server and select DB
// ..
// your query will select to edit record by id if you have one
$query = "SELECT name, phone, mail from table where id='$id' ";
$result = mysql_query($query, $link);
$row = mysql_fetch_array($result);
?><form action="edit.php" method="POST">
<input type="text" name="name" value="<?php echo $row['name']; ?>">
<input type="text" name="phone" value="<?php echo $row['phone']; ?>">
<input type="text" name="mail" value="<?php echo $row['mail']; ?>">
<input type="hidden" name="id" value="<?php echo $id; ?>">
<input type="submit" name="submit" value="Edit">
</form>
edit.php
<?php
// connect to DB server and select DB
....
// validate form data
// ...
$query = "UPDATE table SET name='$_POST[name]', phone='$_POST[phone]', name='$_POST[mail]' WHERE id='$_POST[id]' ";
// ...
?>
-Mitko Kostov