Previous or Next? Paginating Records with PHP - Part 2 - Defining the "displayRecords()" method (
Page 4 of 6 )
The "displayRecords()" method is the workhorse of the class, and accepts one parameter, $page, which determines which page of the retrieved records we want to see. So, let's start by defining its signature and then explain how it works:
function displayRecords($page){
// calculate number of pages
$numPages=ceil(count($this->totalRecs)/$this->numRecs);
// validate page pointer
if(!preg_match("/^\d{1,2}$/",$page)
||$page<1||$page>$numPages){
$page=1;
}
// retrieve corresponding records from flat file
$records=array_slice($this->totalRecs,($page-1)*$this-
>numRecs,$this->numRecs);
foreach($records as $row){
$columns=explode('|',$row);
foreach($columns as $column){
$this->output.=$column.' ';
}
$this->output.='<br />';
}
// create previous link
if($page>1){
$this->output.='<a href="'.$_SERVER['PHP_SELF'].'?
page='.($page-1).'"><<Previous</a> ';
}
// create intermediate links
for($i=1;$i<=$numPages;$i++){
($i!=$page)?$this->output.='<a href="'.$_SERVER
['PHP_SELF'].'?page='.$i.'">'.$i.'</a> ':$this-
>output.=$i.' ';
}
// create next link
if($page<$numPages){
$this->output.=' <a href="'.$_SERVER
['PHP_SELF'].'?page='.($page+1).'">Next>></a> ';
}
// return final output
return $this->output;
}
As I said previously, the method accepts the $page parameter, which is the page pointer to determine which page we wish to view. However, before any validation process takes place, it calculates the number of pages needed to display the complete number of records. This value is obtained with the following lines:
// calculate number of pages
$numPages=ceil(count($this->totalRecs)/$this->numRecs);
Here we're dividing the total number of records read from the file by the number of records per page. Using ceil(), we round a decimal number up; in this way 3.25 becomes 4. Doing so, we get an integer value as the number of pages to be used.
Having obtained the number of pages, the method is now capable of validating the $page parameter. Maybe you're asking… why should I check out the validity of this parameter? The answer is that we don't want this value to be tampered with by external code. We're using the same technique shown in the first article. It's really funny to see how many websites fail to validate page pointers, and end up modifying paging links according to code injected through the querystring, even if they're using a URL rewriter. We don't want this to happen, so the method checks if the $page pointer is valid, like this:
if(!preg_match("/^\d{1,2}$/",$page)
||$page<1||$page>$numPages){
$page=1;
}
Any attempt to tamper with the page pointer will result in a value of 1. Doing so, the method will display the first page. Simple and straightforward, right?
Are you getting tired of long explanations and want to see the class in action? So am I! But there are a few lines of code that still need to be explained. Just be a bit patient and keep reading.
