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Date Published: 2000-05-01
Written for the Perl Archive by Ray Street
You have often seen search results split into pages with 10 results per page - all the search engines do
this. There are links near the foot of each page to the next and previous pages so when you click on them
you jump to the required page.
How can this be done in Perl?
It's easy - I'll show you a simple way to do this.
First of all, you need your results. You usually get these from a file of some kind. For the purposes of
this article, I'll assume that you've found all of the details and have them stored in an array called
@results (this array would probably hold the keys of the file records so
that you can access the records again when you show the results pages). You've also stored the number
of results in $result_count.
Now decide how many results in a page - it's usually 10 but if you're showing a lot of graphics you
might want to use 5. Put the count into $pagesize
($pagesize = 10;) - if you use $pagesize
throughout the script then you can experiment with different numbers of results on a page by changing
this single line of code.
Work out how many pages you're going to show as follows:-
if ($result_count != 0) {
$pagecount = int($result_count / $pagesize);
if (($pagecount * $pagesize) != $result_count) {
$pagecount++;
}
}
Now you want to know which page of results you're about to show. The links at the foot of the page are
going to call this same script with a field called reqpage - if reqpage is not defined (which means
that this is the first time that the current script has been used) then set
$reqpage to 1, otherwise set $reqpage to
the input field value.
Now work out which is the first and last result that you want to show by using the
$reqpage and $pagesize values.
$firstresult = (($reqpage - 1) * $pagesize) + 1;
$lastresult = $firstresult + $pagesize - 1;
if ($lastresult > $result_count) {
$lastresult = $result_count;
}
The adjustment of $lastresult stops you from running off the end of
the array on the last page if there are not $pagesize number of results
to show.
You can now output your results. This is going to vary for every application but usually involves
you writing a processing loop to work from the $firstresult element in the
@results array to the $lastresult element
(reading the file/database again as necessary and generating the HTML code). If you want, you can output a
heading before the results saying something like
"Results $firstresult to $lastresult of $result_count" so that the total
number of results is shown and the current position within the result pages is obvious - this is a very
good idea if the web page is more than a screen in size (a lot of results pages are more than a screen).
So the results are shown and now you need to put in the links.
I've chosen to use text words ("Previous" and "Next") with arrows for people who want to work backwards
and forwards through the results without worrying what the current page is - you could equally use a
graphic. The word "Previous" is not shown if you're on the first page and "Next" is not shown if you're
on the last page.
I also show the current page number as bold without it being a link - this lets the person easily see
what page they're on.
First of all, set up the "Previous" and "Next" details:-
$prev_page = $reqpage - 1;
$next_page = $reqpage + 1;
if ($reqpage == 1) {
$prev_link = "";
} else {
$prev_link = " <a href=\"http://domain/cgi-bin/results.cgi?reqpage=$prev_page&pagesize=$pagesize\">" . "PREVIOUS" . "</a>";
}
if ($reqpage == $pagecount) {
$next_link = "";
} else {
$next_link = " <a href=\"http://domain/cgi-bin/results.cgi?reqpage=$next_page&pagesize=$pagesize\">" . "NEXT" . "</a>";
}
You're now ready to create the links - remember that you don't do this if there is only one page of
results (a bit pointless really):-
if ($pagecount > 1) {
$pagelinks = $prev_link;
$pageno = 0;
while ($pageno < $pagecount) {
$pageno++;
if ($pageno == $reqpage) {
$thislink = " <b>$pageno</b> ";
} else {
$thislink = " <a href=\"http://domain/cgi-bin/results.cgi?reqpage=$pageno&pagesize=$pagesize\">" . $pageno . "</a>";
}
$pagelinks = $pagelinks . $thislink;
}
$pagelinks = $pagelinks . " " . $next_link;
} else {
$pagelinks = "";
}
So all you have to do now is output the $pagelinks variable to the HTML and
the links are there.
That's it. Told you it was easy.
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