# Use a PHP Array to Implement the Pagination Function

On a blog's front page, the pagination is a common way to navigate users 
from on page to another to browse the list of posts. 
According to the page number, we need to get the relevant posts'
meta data, e.g. titles, descriptions, dates, authors and tags.

We can use an `array` to store each post's meta data, for example:
```php
$post = array(
            'Date' => '2020-09-01',
            'Title' => 'Java programming tutorial 1',
            'Description' => 'Introduction to Java programming',
            'Author' => 'David',
            'Tag' => 'Java, Programming, Tutorial'
        );
```

Suppose all posts' meta data is retrieved and stored in the array `$posts`,
we can then get the relevant posts' meta data based on the input page number.
```php
const PAGE_LIMIT = 10;

function getPagination($posts, $page_number) {
    
    $total_pages = ceil(count($posts) / PAGE_LIMIT);
    $offset = ($page_number - 1) * PAGE_LIMIT;
    $paged_posts = array_slice($posts, $offset, PAGE_LIMIT);    
    
    $show_pages = array('Total pages' => $total_pages,
                        'Paged posts' => $paged_posts    
                  );
                  
    return $show_pages;
    
}
```

In the above code snippet, we define the constant `PAGE_LIMIT`
for the number of posts displayed on each page. 
In this example, we allow `10` posts to be displayed on each page.
The function `getPagination($posts, $page_number)`
gets the relevant posts' meta data based on the input page number `$page_number`.
First, we calculate the total number of pages `$total_pages` for all posts.
Then, we calculate the offset, i.e. the start point, based on the input page number `$page_number`.
The PHP function `array_slice()` get the sequence of elements from the 
input array `$posts` according to the offset `$offset`
and the length `PAGE_LIMIT`.
Finally, we return an array `$show_pages` with the total number of pages and the posts that need to be displayed .

To try the function `getPagination($posts, $page_number)`, 
we can first generate the sample data.


```php
$template = array(
            'Date' => '2020-09-01',
            'Title' => 'Java programming tutorial',
            'Description' => 'Introduction to Java programming',
            'Author' => 'David',
            'Tag' => 'Java, Programming, Tutorial'
        );
        
$posts = array();

for ($i = 1; $i < 37; $i++) {
    $post = $template;
    $post['Title'] = $post['Title'].' '.$i;
    array_push($posts, $post);
} 
```

In the above code snippet, we create a template `$template` for a post's meta data.
In the `for` loop, we generate total `36` posts' meta data and 
store it in the array `$posts`. 

Suppose we want to get the 4th page of the posts, we can do as below:
```php
$page_number = 4;
$show_pages = getPagination($posts, $page_number);

echo 'Total pages: ';
echo $show_pages['Total pages'].'<br>';
echo 'Current page: '.$page_number.'<br>';
print_r($show_pages['Paged posts'][0]['Title']);
``` 
It will output:
```html
Total pages: 4
Current page: 4
Java programming tutorial 31
```

Thanks for reading!
To find more programming tutorials, please visit: [CodeBilby.com](https://www.codebilby.com)