Prev and Next buttons - php

Question

I'm new and still learning php&mysql. Search all day and tried different tutorials but nothing happen. So far I have only this with which I fetch text from my DB. How can I make prev and next buttons here?
if($q = mysqli_query($con, 'SELECT * FROM joke WHERE `id` = ' . mysqli_real_escape_string($con,$_GET['id']))){
if($row = mysqli_fetch_array($q)){
echo nl2br($row['text']);
echo '<div id="data">Date ' . $row['date'] . "</div>';
} else {
echo 'Not found';
}
} else {
echo mysqli_error($con);
}
echo "</div>";
$query = "select * from joke order by RAND() LIMIT 1";
$result = mysqli_query($con, $query) or die("Query failed: " . mysqli_errno($con));
while ($row = mysqli_fetch_array($result, MYSQL_BOTH)){
echo 'Random';
}

Answer 1

if i understand you correctly you want to display the next and previous joke based on id,
so you want to select max(id) from joke where id < the current id
and ... select min(id) from joke where id > the current id
$currentId = mysqli_real_escape_string($con,$_GET['id']);
if($q = mysqli_query($con, 'SELECT *,
(SELECT IFNULL(max(id),-1) FROM joke WHERE `id` < '.$currentId.') as previousid,
(SELECT IFNULL(min(id),-1) FROM joke WHERE `id` > '.$currentId.') as nextid
FROM joke WHERE `id` = ' . $currentId)){
if($row = mysqli_fetch_array($q, MYSQL_BOTH)){
echo nl2br($row['text']);
echo '<div id="data">Date ' . $row['date'] . '</div>';
if ($row['previousid'] > -1){
echo 'Previous';
}
if ($row['nextid'] > -1){
echo 'Next';
}
} else {
echo 'Not found';
}
} else {
echo mysqli_error($con);
}
echo "</div>";
$query = "select * from joke order by RAND() LIMIT 1";
$result = mysqli_query($con, $query) or die("Query failed: " . mysqli_errno($con));
while ($row = mysqli_fetch_array($result, MYSQL_BOTH)){
echo 'Random';
}