how to update arrayed fields in php and mysql

[elie]

good day to all of you!

my page is all about asking a user to input any number of 'equipments' and the output will produce number of sets of fields which the user inputted on the previous page.. i have already the scripts on inserting and viewing these records using mysql and php; these codes are working well already...

(inventory1) -- after the user inputted the number
[code]
.
.
.
<?php

for($i=0; $i<$num; $i++)
{
    echo "
    <tr><td align=center><input type='text' name='field_a[]' size='15'/></td>
        <td align=center><input type='text' name='field_b[]' size='15'/></td>
        <td align=center><input type='text' name='field_c[]' size='25'/></td>
        <td align=center><input type='text' name='field_d[]' size='15'/></td>
        <td align=center><input type='text' name='field_e[]' size='15'/></td>
        <td align=center><input type='text' name='field_f[]' size='25'/></td></tr>
    ";
}
?>
.
.
.
[/code]


(inventory2.php) -- the records being inserted in database
[code]
<?php
$field_a = $_POST['field_a'];
$field_b = $_POST['field_b'];
$field_c = $_POST['field_c'];
$field_d = $_POST['field_d'];
$field_e = $_POST['field_e'];
$field_f = $_POST['field_f'];
$num = $_POST['num'];
foreach($field_a as $key => $val)
{
$sql="INSERT INTO inventory (field_a, field_b, field_c, field_d, field_e, field_f, title) VALUES ('".$val."','".$field_b[$key]."','".$field_c[$key]."','".$field_d[$key]."','".$field_e[$key]."','".$field_f[$key]."', '$title')";

$connection = mysql_connect("localhost","root","") or die ("Couldn't connect to server.");
$db = mysql_select_db("setup", $connection) or die ("Couldn't select database.");
mysql_query($sql) or die(mysql_error());
}
.
.
.
[/code]


(view.php) -- viewing them
[code]
<?php
include("config.php");

$query = "SELECT * FROM inventory where title='$title'";
$result = mysql_query($query) or die(mysql_error());
if($result && mysql_num_rows($result) > 0)
{
     while($row = mysql_fetch_array($result))
     {
          extract($row);
echo "
<tr>
<td>$field_a<br /></td>
<td>$field_b<br /></td>
<td>$field_c<br /></td>
<td>$field_d<br /></td>
<td>$field_e<br /></td>
<td>$field_f<br /></td>
</tr>
";          
     }
}
[/code]


my problem now is how to update the arrayed fields?? in mysql and php?? please help!