Problems with pagination - php

Question

I am working on a university project, which is based on e-shopping, i tried this code to implement my result, this gives no error but it does not work when I press next page link or "button" please help any help would be appreciated
<?php
$con = mysqli_connect("localhost","root","","php184_proj_db");
// Check connection
if (mysqli_connect_errno($con))
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
if (!(isset($pagenum)))
{
$pagenum = 1;
}
//Here we count the number of results
//Edit $qry to be your query
$qry = "SELECT * FROM posts";
$result = mysqli_query($con,$qry);
$row = mysqli_num_rows($result);
//This is the number of results displayed per page
$page_rows = 5;
//This tells us the page number of our last page
$last = ceil($row/$page_rows);
//this makes sure the page number isn't below one, or more than our maximum pages
if ($pagenum < 1)
{
$pagenum = 1; //Pagination of MySQL Query Results Setting the Variables
}
elseif ($pagenum > $last)
{
$pagenum = $last;
}
//This sets the range to display in our query
$max = 'limit ' .($pagenum - 1) * $page_rows .',' .$page_rows;
$j=0;
$qry = "SELECT * FROM posts $max";
$result = mysqli_query($con,$qry);
while($row = mysqli_fetch_array($result))
{
$j++;
echo "<p>";
// This shows the user what page they are on, and the total number Query and Results of pages
echo " --Page $pagenum of $last--
<p>";
// First we check if we are on page one. If we are then we don't need a
//link to the previous page or the first page so we do nothing. If we aren't
//then we generate links to the first page, and to the previous page.
if ($pagenum == 1)
{
}
else
{
echo " <a
href='{$_SERVER['PHP_SELF']}?pagenum=1'>
<<-First</a>
";
echo " ";
$previous = $pagenum-1;
echo " <a
href='{$_SERVER['PHP_SELF']}?
pagenum=$previous'> <-Previous</a>
";
}
//just a spacer
echo " ---- ";
//This does the same as above, only checking if we are on the last page,
//and then generating the Next and Last links
if ($pagenum == $last)
{
}
else {
$next = $pagenum+1;
echo " <a
href='{$_SERVER['PHP_SELF']}?pagenum=$next'>Next
-></a> ";
echo " ";
echo " <a
href='{$_SERVER['PHP_SELF']}?pagenum=$last'>Last
->></a> ";
}
?>

Answer 1

If you visit this URL: http://example.com/somepage.php?key=val, you don't automatically get a variable $key inside PHP. Instead, you have to use $_GET['key'], which will hold the value. (in this case: 'val')
So, somewhere in the beginning of your code, add the following:
if (isset($_GET['pagenum']) && $_GET['pagenum'] >= 1) {
$pagenum = (int) $_GET['pagenum'];
} else {
$pagenum = 1;
}
Not only does this create the $pagenum variable and give it the value from the URL, it also makes sure that the value is a valid number. If not, or if the URL doesn't contain a pagenum, it is set to 1.
Possible scenario's:
pagenum contains not an integer, but a string (might even be a SQL injection attempt)
pagenum is a negative number, or 0
pagenum isn't set at all
In all of the above cases, pagenum is set to 1.
If pagenum contains a float (for instance 1.5.), the value will be cast to an integer. In the case of 1.5, pagenum will become 1.
Remember, always make sure you sanitize user input.