Trouble with multiple PHP/SQL queries?

I'm attempting to build a website with various PHP/SQL functions for a fictional motorhome dealership as part of an assignment. One of the required functions is to update entries in the SQL database, which is currently giving me a single, large problem.
The update process is made up of 3 pages, the first has a dynamically filled dropdown menu that populates with all the ID numbers of all the database entires. When one is chosen and the 'submit' button is pressed, the next page comes up. Here, with the exception of the ID number, all the information in the appropriate row is displayed in it's own text field. This works no problem, however, when the submit button on this page is hit, I'm given the error code 'Undefined index: motorID' and I can't figure out why.
This is my current PHP coding:
Page 1:
<form name = "UpdateMotorhome" id = "UpdateMotorhome"
action = "adminUpdateQuery1.php" method = "post">

<?php
include 'database_conn.php';
$sql = "SELECT motorID FROM motorhomes";
$result = mysql_query($sql)
or die(mysql_error());

$options = "";

while ($row = mysql_fetch_array($result)) {

$motorID = $row['motorID'];
$options.= "<OPTION VALUE=\"$motorID\">".$motorID.'</option>…
}
?>

<SELECT NAME=motorID>
<OPTION VALUE=0>Choose
<?=$options?>
</SELECT>
<input type = "submit" value = "submit" />
</form>

Page 2:
<?php

$mID = $_REQUEST['motorID'];

include 'database_conn.php';
$sql = "SELECT * FROM motorhomes WHERE motorID = '$mID'";
$queryresult = mysql_query($sql)
or die(mysql_error());

while ($row = mysql_fetch_assoc($queryresult)){
$motorID = $row['motorID'];
$manufacturer = $row['manufacturer'];
$model = $row['model'];
$year = $row['year'];
$engine = $row['engine'];
$berths = $row['berths'];
$mileage = $row['mileage'];
$price = $row['price'];
$layout = $row['layout'];
$ownership = $row['ownership'];
$description = $row ['description'];
?>

<form name = "UpdateMotorhomePart2" id = "UpdateMotorhomePart2"
action = "adminUpdateQuery2.php" method = "post">

<?php
echo "<div id=\"result\">";
echo "Motorhome ID: $motorID
";
echo "Manufacturer: <input type = \"text\" name = \"manufacturer\" value=\"$manufacturer\">
";
echo "Model: <input type = \"text\" name = \"model\" value=\"$model\">
";
echo "Year: <input type = \"text\" name = \"year\" value=\"$year\">
";
echo "Engine: <input type = \"text\" name = \"engine\" value=\"$engine\">
";
echo "Berths: <input type = \"text\" name = \"berths\" value=\"$berths\">
";
echo "Mileage: <input type = \"text\" name = \"mileage\" value=\"$mileage\">
";
echo "Price: <input type = \"text\" name = \"price\" value=\"$price\">
";
echo "Layout: <input type = \"text\" name = \"layout\" value=\"$layout\">
";
echo "Ownership: <input type = \"text\" name = \"ownership\" value=\"$ownership\">
";
echo "Description: <input type = \"text\" name = \"description\" value=\"$description\">
";
echo "<hr />";
echo "</div>";
}
?>

<input type = "submit" value = "submit" />

</form>

Page 3:
<?php
include 'database_conn.php';

$motorID = $_REQUEST['motorID']; //Line error keeps occuring on
$manufacturer = $_REQUEST['manufacturer'];
$model = $_REQUEST['model'];
$year = $_REQUEST['year'];
$engine = $_REQUEST['engine'];
$berths = $_REQUEST['berths'];
$mileage = $_REQUEST['mileage'];
$price = $_REQUEST['price'];
$layout = $_REQUEST['layout'];
$ownership = $_REQUEST['ownership'];
$description = $_REQUEST['description'];

$sql = "UPDATE motorhomes SET manufacturer = '$manufacturer', model = '$model', year = '$year',
engine = '$engine', berths = '$berths', mileage = '$mileage', price = '$price', layout = '$layout',
ownership = '$ownership', description = '$description' WHERE motorID = '$motorID'";
$queryresult = mysql_query($sql)
or die(mysql_error());

echo "Record Updated";

?>

Thanks for any advise in advance.

I tried a similar set up with the Remove from database function (without editable data on 2nd page) that gave me the same problem. I eventually removed the 2nd page and the function started working correctly.

 

A lot of small logic and syntax errors in this code.
Let's rewrite it as a single scrpt!

NEWSCRIPT.PHP
require_once ("database_conn.php");
<head>
<?php
function select_vehicle()
{
$txt = "<form name = \"UpdateMotorhome\"
action = \"".$_SERVER['PHP_SELF']."\" method = \"POST\">";
$link = dbconnect(); // whatever function to connect and
select db in the file database_conn.php
$sql = "SELECT `motorID` FROM `motorhomes`";
$result = mysql_query($sql) or die(mysql_error());
$txt .= "<select name=\"vehicle\">";
while ($row = mysql_fetch_array($result))
{
$motorID = $row['motorID'];
$txt .= "<option value=\"".$motorID."\">";
$txt .= $motorID."</option>";
}
mysql_free_result($result);
mysql_close($link);
$txt .= "</select>";
$txt .= "<input type = \"submit\" value = \"submit\" />";
$txt .= "</form>";
return($txt);
}
function edit_vehicle($mID)
{
$link = dbconnect();
$sql = "select * from `motorhomes` where `motorID` = '".$mID."' limit 1";
// Not syntax! "`" to enclose table and fields name
// there whould only be ONE motorID
$queryresult = mysql_query($sql)
or die(mysql_error());
$row = mysql_fetch_array($queryresult);
$txt = "<form name = \"UpdateMotorhomePart2\"
action = \"".$_SERVER['PHP_SELF']."\" method = \"post\">";
$txt .= "Motorhome ID: ".$row['motorID']."<br>";
$txt .= "Manufacturer: <input type = \"text\" name = \"manufacturer\"
value=\"".$row['manufacturer']."\"><br…
$txt .= "Model: <input type = \"text\" name = \"model\"
value=\"".$row['model']."\"><br>";
$txt .= "Year: <input type = \"text\" name = \"year\"
value=\"".$row['year']."\">";
$txt .= "Engine: <input type = \"text\" name = \"engine\"
value=\"$row['engine']."\"><br>";
$txt .= "Berths: <input type = \"text\" name = \"berths\"
value=\"".$row['berths']."\"><br>";
$txt .= "Mileage: <input type = \"text\" name = \"mileage\"
value=\"".$row['mileage']."\"><br>";
$txt .= "Price: <input type = \"text\" name = \"price\"
value=\"".$row['price']."\"><br>";
$txt .= "Layout: <input type = \"text\" name = \"layout\"
value=\"".$row['layout']."\"><br>";
$txt .= "Ownership: <input type = \"text\" name = \"ownership\"
value=\"".$row['ownership']."\"><br>";
$txt .= "Description: <input type = \"text\" name = \"description\"
value=\"".$row['description']."\"><br>…
$txt .= "<input type=\"hidden\" name=\"motid\" value=\"".$mID."\" />";
$txt .= "<input type = \"submit\" value = \"submit\" />";
$txt .= "</form>";
return($txt);
}
function update_vehicle($_POST)
{
$link = dbconnect();
$sql = "update `motorhomes` SET `manufacturer` = '".$_POST['manufacturer']."',
`model` = '".$_POST['model']."', `year` = '".$_POST['year']."',
`engine` = '".$_POST['engine']."', `berths` = '".$_POST['berths']."',
`mileage` = '".$_POST['mileage']."', `price` = '".$_POST['price']."',
`layout` = '".$_POST['layout']."', `ownership` = '".$_POST['ownership']."',
`description` = '".$_POST['description']."' where `motorID` = '".$motid."' limit 1";
$queryresult = mysql_query($sql)
or die(mysql_error());
mysql_close($link);
return ("Record Updated");
}
?>
</head>
<body>
<?php
if (isset($_POST['motid']))
{
echo (update_vehicle($_POST));
unset($POST['motid']);
}
else if (isset($_POST['vehicle']))
{
echo (edit_vehicle($_POST['vehicle']));
unset($_POST['vehicle']);
}
else
{
echo (select_vehicle());
}
?>
</body>

(Untested)

 

motorID had to be part of your form on page 2.

 

At first, I misunderstood what this answer meant, but after a few minutes got the function working correctly. Thanks for your help guys!