Get result from SQL Query - php

Question

I've got a MySQL query based on a database of ship information, this includes a field ship_name and the key ship_id.
I've written a query which uses the current_ship_id of the page, and finds the next ship based on the alphabetical list of ship_names.
This all works fine, HOWEVER, I'm trying to create a link using the below code in the 'IF' statement.
header("Location: shipinfo.php?ship_id=$next_ship_id");
What I don't know how to do is define the variable next_ship_id. I tried the line:
$next_ship_id = ($ship_id);
In theory, I want to get the result of the query $sql (of which I know there is only one result) and find it's ship_id.
How do I do that please?
$sql = " SELECT ship_infomation.ship_id
FROM ship_infomation
INNER JOIN (
SELECT ship_name
FROM ship_infomation
WHERE ship_id = $current_ship_id
) As current_ship
ON ship_infomation.ship_name < current_ship.ship_name
ORDER BY ship_infomation.ship_name ASC
LIMIT 1";
// echo "<br /><br />$sql<br /><br />";
$ships = mysql_query($sql, $ships) or die(mysql_error());
$row_ships = mysql_fetch_assoc($ships);
$totalRows_ships = mysql_num_rows($ships);
$next_ship_id = ($ship_id);
if ($totalRows_ships = 1)
{
header("Location: shipinfo.php?ship_id=$next_ship_id");
}
else
{
// remain on current page
}

Answer 1

For the next ship use:
SELECT ship_id
FROM ship_infomation
WHERE ship_id = (SELECT min(ship_id)
FROM ship_infomation
WHERE ship_id > $current_ship_id)
LIMIT 1
For the previous ship use:
SELECT ship_id
FROM ship_infomation
WHERE ship_id = (SELECT max(ship_id)
FROM ship_infomation
WHERE ship_id < $current_ship_id)
LIMIT 1
And at your code change this:
$ships = mysql_query($sql, $ships) or die(mysql_error());
$row_ships = mysql_fetch_assoc($ships);
$totalRows_ships = mysql_num_rows($ships);
$next_ship_id = ($ship_id);
if ($totalRows_ships = 1)
{
header("Location: shipinfo.php?ship_id=$next_ship_id");
}
else
{
// remain on current page
}
To this:
$ships = mysql_query($sql, $ships) or die(mysql_error());
$row = mysql_fetch_assoc($ships);
$totalRows_ships = mysql_num_rows($ships);
if ($totalRows_ships = 1)
{
header("Location: shipinfo.php?ship_id=" . $row['ship_id']);
}
else
{
// remain on current page
}
For the next and previous, on your code:
$go = isset($_GET['go']) ? $_GET['go'] : 'next';
if ($go == 'next')
$sql = "SELECT ship_id FROM ship_infomation WHERE ship_id = (SELECT min(ship_id) FROM ship_infomation WHERE ship_id > ". mysql_real_escape_string($current_ship_id) . ") LIMIT 1";
else
$sql = "SELECT ship_id FROM ship_infomation WHERE ship_id = (SELECT max(ship_id) FROM ship_infomation WHERE ship_id < ". mysql_real_escape_string($current_ship_id) . ") LIMIT 1";
And on your URL have it like this for the next ship:
http://mysite.com/ships.php?current_ship_id=15&go=next
And like this for the previous:
http://mysite.com/ships.php?current_ship_id=15&go=previous
If the go is not specified it will go to the previous ship by default.
There is no more support for mysql_* functions, they are officially deprecated, no longer maintained and will be removed in the future. You should update your code with PDO or MySQLi to ensure the functionality of your project in the future.