Little help in SQL

[Robin H]

I think you only need to update the 'update_ac.php' file:

<?php
//I assume this is update_ac.php
$host="localhost"; // Host name 
$username=""; // Mysql username 
$password=""; // Mysql password 
$db_name="test"; // Database name 
$tbl_name="test_mysql"; // Table name 

// Connect to server and select database.
mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("cannot select DB");

// update data in mysql database 
$sql='UPDATE '.$tbl_name.' SET username="'.mysql_real_escape_string($_POST['username']).'", password="'.mysql_real_escape_string($_POST['password']).'", email="'.mysql_real_escape_string($_POST['password']).'" WHERE id='.intval($_POST['id']);

/*
this query might work aswell ( note the different type of quotes used ) but use the one above
$sql="UPDATE $tbl_name SET username='mysql_real_escape_string($_POST['username'])', password='mysql_real_escape_string($_POST['password'])', email='mysql_real_escape_string($_POST['password'])' WHERE id=intval($_POST['id'])";

*/

/*
    In php these are thesame:

    $cool = "awesome";

    echo "lol this is $cool";  <- this shows : lol this is awesome
    echo 'lol this is '. $cool;  <- this shows : lol this is awesome
*/

/*
    the dot ( . ) acts as glue.
    For example:

    $this = 'Hi';
    $still = ', how';
    $works = ' are you';

    echo $this . $still . $works . 'doing?'; <- This shows : Hi, how are you doing?
    
    so does this btw:
    echo $this.$still.$works.'doing?'; ( the space doesn't matter )
*/

/*
    Now about the $_POST[''] variable I used in your query ( line 14 )
    
    Whenever you submit a form [ remember the <form method="post".. u used in your HTML ? ] to a script, the data you send
    gets stored in the $_POST array.
    
    For example:
    <input type="text" name="KWWHunction" /> ( let's assume you entered sucks and pressed submit )
    
    it will be handled in the script with:
    $_POST['KWWHunction']
    
    So if you do this in your script:
    
    echo $_POST['KWWHunction'];
    
    That will show the word sucks
*/

$result=mysql_query($sql);

// if successfully updated. 
if($result){
echo "Successful";
echo "<BR>";
echo "<a href='list_records.php'>View result</a>";
}

else {
echo "ERROR";
}

?>

edit:
Added a bit of info as it seems you are quite new with this.
Not sure if what I said is correct, i'm really tired atm