What is wrong with this pagination? - php

Question

What is wrong with this code? When I click on 'Next' button it shows empty page and broke my web design? I've trying to figure it out all day but no luck.
<?php
if(isset($_GET['joke_id'])){
$joke_id = $_GET['joke_id'];
$qry = "SELECT * FROM joke WHERE joke_cat = '$joke_id'";
$result = mysqli_query($con, $qry) or die("Query failed: " . mysqli_errno($con));
$line = mysqli_fetch_array($result, MYSQL_BOTH);
if (!$line) echo '';
$previd = -1;
$currid = $line[0];
if (isset($_GET['id'])) {
$previous_ids = array();
do {
$previous_ids[] = $line[0];
$currid = $line[0];
if ($currid == $_GET['id']) break;
$previd = end($previous_ids);
$line = mysqli_fetch_array($result, MYSQL_BOTH);
} while ($line);
}
if ($line) {
echo "<div id=\"box\">";
echo nl2br($line['text']) . "<br /><br />";
echo "</div>";
}
else echo 'Is empty<br/>'; **<------ HERE**
if ($previd > -1)
echo '<span>Prev</span>';
echo str_repeat(' ', 5);
$line = mysqli_fetch_array($result, MYSQL_BOTH);
$query = "select * from joke WHERE joke_cat = '$joke_id' 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';
}
echo str_repeat(' ', 5);
if ($line) echo '<span>Next</span><br /><br />';
echo "</div>\r";
}
?>
Also on the line else echo 'Is empty<br/>'; doesn't matter if there is something .. always shows me 'Is empty'..
UPDATE:
databases are:
joke
id
text
date
joke_cat
and cat_joke is
joke_id
joke_name

Answer 1

change this line:
echo 'Random';
To: not ? after cat_id='.$joke_id.' you need to change &
echo 'Random';
Note: also change next and prev code also...

Answer 2

Your last assigment to $line is null .Therefore you should check in your if not $line but the $previous_ids[] or $currid or the others.