mysqli setting next and previous button using id - php

Question

I would like to make a previous and next button to scroll through the database using ID. This is my code when I am still using mysql. Right now it is changed to mysqli so I have no idea whether this code still works or not, because I keep getting null.
function getNavID($id) {
$result4= mysqli_query("SELECT
( SELECT id FROM products_list
WHERE id > '$id' LIMIT 1 ) AS nextValue,
( SELECT id FROM products_list
WHERE id < '$id' ORDER BY id DESC LIMIT 1 ) AS prevValue
FROM products_list
LIMIT 1");
if ($resultID = mysqli_fetch_array($result4)) {
return $resultID;
}
else {
return NULL;
}
}
$LinkID = getNavID($id);
if (!is_null($LinkID['prevValue']))
{
?>
Previous
<?php
}
else if (!is_null($LinkID['nextValue']))
{
?>
Next
<?php
}
else
{
echo "No Entries";
}
Besides changing mysql_query to mysqli_query, is there anything that I need to change too? Thanks in advance for the help!

Answer 1

try this :
global $pdo;
$id = $the_selected_id;
$stmt_a = $pdo->prepare("
(SELECT * FROM images WHERE id < ? ORDER BY id DESC LIMIT 1)
UNION (SELECT * FROM images WHERE id = (SELECT MAX(id) FROM images)) LIMIT 1");
$stmt_b = $pdo->prepare("
(SELECT * FROM images WHERE id > ? ORDER BY id ASC LIMIT 1)
UNION (SELECT * FROM images WHERE id = (SELECT MIN(id) FROM images)) LIMIT 1");
// $vars = array(':id' => $id);
$prev = $stmt_a->execute(array( (int)$id ));
$next = $stmt_b->execute(array( (int)$id ));
if ($stmt_a->rowCount() > 0) {
while($row = $stmt_a->fetch(PDO::FETCH_ASSOC)) {
echo 'Previous';
}
} else {
echo 'no previous';
}
if ($stmt_b->rowCount() > 0) {
while($row = $stmt_b->fetch(PDO::FETCH_ASSOC)) {
echo 'Next';
}
} else {
echo 'no next';

Answer 2

entre your db conection befor sentax like this:
<?
//enter your MySQL database host name, often it is not necessary to edit this line
$db_host = "localhost";
//enter your MySQL database username
$db_username = "your user name";
//enter your MySQL database password
$db_password = "your passwor";
//enter your MySQL database name
$db_name = "your db name";
//URL to the the site
$ScriptPath = "http://www.your-site.com/";
$db = mysqli_connect($db_host, $db_username, $db_password) or die("Error " . mysqli_error($db));
mysqli_select_db($db, $db_name) or die("Error " . mysqli_error($db));
function getNavID($id) {
$result4= mysqli_query($db, "SELECT
( SELECT id FROM products_list
WHERE id > '$id' LIMIT 1 ) AS nextValue,
( SELECT id FROM products_list
WHERE id < '$id' ORDER BY id DESC LIMIT 1 ) AS prevValue
FROM products_list
LIMIT 1");
if ($resultID = mysqli_fetch_array($db, $result4)) {
return $resultID;
}
else {
return NULL;
}
}
$LinkID = getNavID($id);
if (!is_null($LinkID['prevValue']))
{
?>
Previous
<?php
}
else if (!is_null($LinkID['nextValue']))
{
?>
Next
<?php
}
else
{
echo "No Entries";
}
?>