0

I'm trying to make a simple blog. On the bottom of the page content i placed pagination which displays links to next and previous blog entry, with the blog title in the link that I'm getting from the database table called "pages", column "menu_name". I did this by first making a query and creating an array through a function in the class called "Blog" and then setting some variables:

$sql = "SELECT * FROM pages ";
$sql .= "ORDER BY id DESC ";
$pages = Blog::find_by_sql($sql);
$blog_page = reset($pages);
$page_id = Blog::find_by_id(isset($_GET['page']) ? $_GET['page'] : $blog_page->id);

Then I made the code for the previous blog link as follows:

public function pagination_previous(){
    global $address; //$address = "list_blogs.php?page=";
    global $page_id;
    global $pagination; //a class for storing functions that handle pagination
    global $pages;
    if($pagination->has_next_page()){
        echo "\n        <a class=\"olderblog\" href=" . $address;
        echo $pagination->next_page();
        echo " title=\"Newer Blog\">&laquo; ";
        foreach($pages as $page => $value){
            if($page_id->id + 1 == $value->id){
                echo $value->menu_name;
            }
        };
        echo "</a> ";   
    }else{
        echo "";
    }   
}

This is the function has_next_page()

public function has_previous_page(){
    return $this->previous_page() >= 1 ? true : false;  
}

and this is previous_page():

public function previous_page(){
    global $blog;
    return $this->current_page - 1;
}

This worked great until I decided to make admin area from where I can delete blog entries. The problem starts when I delete a blog entry with id let's say 6. Since there is no more item with id=6 in the database table "pages", the links to next or previous page on the pages that came before and after the missing page are empty but still point to the page=6 since has_previous_page() subtracts 1 from $current_page. I half-way figured out a way out of this mess by setting the pagination_next() function like this:

public function pagination_next(){
    global $address;
    global $pagination;
    global $page_id;
    global $pages;
    if($pagination->has_previous_page()){
        foreach($pages as $page => $value){
            if($page_id->id - 1 == $value->id){

                echo "\n        <a class=\"newerblog\" href=" . $address;
                echo $value->id;
                echo " title=\"Older Blog\">";
                echo $value->menu_name;
                break;
            }

        }
        echo " &raquo;</a> ";   
    }else{
        echo "";
    }   
}

This however still does not work because of the if condition inside the foreach loop. I need to set this condition in both pagination_previous() and pagination_next() to reference the next and previous array item based on its array index ($page), not on the id ($value->id) but I can't figure this out for the life of me. This is how the array $pages looks like:

Array
(
[0] => Blog Object
    (
        [id] => 8
        [subject_id] => 2
        [menu_name] => Aliquam sed interdum
        [position] => 4
        [visible] => 1
        [created] => 
        [content] => 
    Aliquam sed interdum tortor. Vivamus et blandit velit...

[1] => Blog Object
    (
        [id] => 7
        [subject_id] => 2
        [menu_name] => Vestibulum ante ipsum
        [position] => 3
        [visible] => 1
        [created] => 
        [content] => 
    Vestibulum ante ipsum primis in faucibus orci luctus et ultrices...

[2] => Blog Object
    (
        [id] => 5
        [subject_id] => 2
        [menu_name] => Praesent massa mi
        [position] => 2
        [visible] => 1
        [created] => 
        [content] => 
    Praesent massa mi, pretium et leo vitae, aliquam...

[3] => Blog Object
    (
        [id] => 4
        [subject_id] => 2
        [menu_name] => Nam interdum tincidunt
        [position] => 1
        [visible] => 1
        [created] => 
        [content] => 
    Nam interdum tincidunt purus quis lacinia. Aliquam erat volutpat.
)

)

Can someone help me out with this?

Thank you all for your answers, but unfortunately none of them helped me solve my problem. After exhausting all options, I definitely concluded that the only way to solve this without messing up the entire code is to figure out how to refer to the next or previous existing $value->id in the if condition without adding or subtracting 1 to get to the next page, because that causes empty links to appear when id is missing from the database. If anyone can solve this puzzle, I will be eternally grateful to that person.

4

4 回答 4

1

您可以previous_page按照以下方式将您的功能转换为：

public function previous_page( )
{
    global $blog;

    $prev = -1; // Initialize

    $arrayKeys = array_keys( $blog );

    rsort( $arrayKeys );    //  Sort keys array in reverse order

    while( list( $key ,$cursor ) = each( $arrayKeys ) )
    {
        if( $cursor == $this->current_page )
        {
            if( list( $key ,$prev ) = each( $arrayKeys ) ) return $prev;
            break;
        }
    }
    return $prev;
}

下面可能会提供更多的理解：

//  Test data

$array = array( 0 => 'Obj 0' ,1 => 'Obj 1' ,2 => 'Obj 2' ,3 => 'Obj 3' ,4 => 'Obj 4' , );


$current = 3;   //  Try with any valid key of the array


//  Get the keys into an array

$arrayKeys = array_keys( $array );

//  Search for next

$next = -1; // Initialize

sort( $arrayKeys ); //  Sort the keys array

while( list( $key ,$cursor ) = each( $arrayKeys ) )
{
    if( $cursor == $current )
    {
        if( list( $key ,$cursor ) = each( $arrayKeys ) )
        {
            $next = $cursor;
        }
        break;
    }
}
//  Search for previous

$prev = -1; // Initialize

rsort( $arrayKeys );    //  Sort keys array in reverse order

while( list( $key ,$cursor ) = each( $arrayKeys ) )
{
    if( $cursor == $current )
    {
        if( list( $key ,$cursor ) = each( $arrayKeys ) )
        {
            $prev = $cursor;
        }
        break;
    }
}

if( $prev <> -1 )   echo '<br>Prev : ' ,$array[$prev];
if( $next <> -1 )   echo '<br>Next : ' ,$array[$next];
于 2013-10-19T22:30:14.433 回答
0

我建议使用 sql 来获取上一个和下一个博客条目

以前的帖子

select * from pages where id = ( select max(id) from pages where id < <current_post_id> )

下一篇文章

select * from pages where id = ( select min(id) from pages where id > <current_post_id> )
于 2013-10-16T18:03:05.370 回答
0

功能齐全的选项可能是在您的博客对象上有一个持久的序列索引字段。分页可以检查上一个/下一个序列索引。您可以编写函数以盲目地假设它们是真正顺序的（并确保在删除帖子时重新索引它们）以便于 +1/-1 实现，或者编写一个找到下一个最高/最低的函数（可能来自 db ）。这将允许您任意移动它们并确保它们的存在。将订单与任意对象 ID 分离。

于 2013-10-16T18:05:22.430 回答
0

在您的数组的 foreach 循环使用 array_values 函数更新您的数组索引之前，它将重新索引您的数组，因此现在您的逻辑将保持不变并正常运行。

于 2013-10-17T08:20:07.207 回答