PHP UPDATE script not working - php

Question

I'm trying to implement an update script on my page but it doesn't work.
I have 2 pages, the 'update.php' page and the 'update_ac.php' page that runs the script after hitting 'submit' on the Form, the code is as below:
update.php
On this page i have this error : Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\update.php on line 16
<?php
$host="localhost"; // Host name
$username="root"; // Mysql username
$password="root"; // Mysql password
$db_name="764503"; // Database name
// Connect to server and select database.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");
// get value of id that sent from address bar
$id=$_GET['id'];
// Retrieve data from database
$result=mysql_query("SELECT * FROM produse WHERE id='$id'");
$rows=mysql_fetch_array($result);
?>
<table width="400" border="0" cellspacing="1" cellpadding="0">
<tr>
<form name="form1" method="post" action="update_ac.php">
<td>
<table width="100%" border="0" cellspacing="1" cellpadding="0">
<tr>
<td> </td>
<td colspan="3"><strong>Update data in mysql</strong> </td>
</tr>
<tr>
<td align="center"> </td>
<td align="center"> </td>
<td align="center"> </td>
<td align="center"> </td>
</tr>
<tr>
<td align="center"> </td>
<td align="center"><strong>titlu</strong></td>
<td align="center"><strong>stare</strong></td>
<td align="center"><strong>pret</strong></td>
<td align="center"><strong>descriere</strong></td>
</tr>
<tr>
<td> </td>
<td align="center">
<input name="titlu" type="text" id="titlu" value="<? echo $rows['titlu']; ?>">
</td>
<td align="center">
<input name="stare" type="text" id="stare" value="<? echo $rows['stare']; ?>" size="15">
</td>
<td>
<input name="pret" type="text" id="pret" value="<? echo $rows['pret']; ?>" size="15">
</td>
<td>
<input name="descriere" type="text" id="descriere" value="<? echo $rows['descriere']; ?>" size="15">
</td>
</tr>
<tr>
<td> </td>
<td>
<input name="id" type="hidden" id="id" value="<? echo $rows['id']; ?>">
</td>
<td align="center">
<input type="submit" name="Submit" value="Submit">
</td>
<td> </td>
</tr>
</table>
</td>
</form>
</tr>
</table>
<?php
// close connection
mysql_close();
?>
update_ac.php
<?php
$host="localhost"; // Host name
$username="root"; // Mysql username
$password="root"; // Mysql password
$db_name="764503"; // Database name
// Connect to server and select database.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");
// update data in mysql database
$sql="UPDATE produse SET titlu='$_POST[titlu]' ,stare='$_POST[stare]' ,pret='$_POST[pret]' ,descriere='$_POST[descriere]' WHERE id='$_POST[id]'";
$result=mysql_query($sql);
// if successfully updated.
if($result)
{
echo "Successful";
}
else
{
echo "ERROR";
}
?>

Answer 1

mysql_query return FALSE when error occurs instead of returning an Array, this test avoid a second (and bigger) error : if FALSE no problem, if an Array you can fetch it ;oP
if ($result) $rows=mysql_fetch_array($result);

Answer 2

This probably means you have an error in your query. If you have an error in your query, it doesnt create a resource to get your data from.
to find an error: add or die(mysql_error()) to your mysql_query command. so you can find out the error.

Answer 3

You have error in your update sql query in the update_ac.php file. So nothing is probably getting updated. You are using the array indexes wrong in the following statement:
$sql="UPDATE produse SET titlu='$_POST[titlu]' ,stare='$_POST[stare]' ,pret='$_POST[pret]' ,descriere='$_POST[descriere]' WHERE id='$_POST[id]'";
$_POST[titlu] should be $_POST['titlu'], $_POST[stare] should be $_POST'stare'] and so on. So the correct query can be as below:
$sql="UPDATE produse SET titlu='".$_POST['titlu']."' ,stare='".$_POST['stare']."' ,pret='".$_POST['pret']."' ,descriere='".$_POST['descriere']."' WHERE id='".$_POST['id']."'";