PHP logic problem

Question

I have a sql table images which has columns id,imagePath,caption``count.

To view those images what i do is, I ask for the page number and query the iamge

$limit=$page-1;
$sel=$mysqli->prepare("SELECT id,imagePath,caption,count from images".
                        " order by id desc limit ".$limit.",1");

This shows images correctly.

But i have another function which shows 4 random thumbnail of that images out of the total images from the database.With those images i also give a href tag so that when a user clicks on that link he is taken to the page of that image.

Now the problem is with those links. Suppose i have images like these in the database

id=1
id=2
id=3
id=4
id=5

To find the page number of the specific id what i do is

$newid=$idOfTheCurrentImage-($idOfTheLastImage-1);

Using this logic i get

id=1  page=5
id=2  page=4
id=3  page=3
id=4  page=2
id=5  page=1

This gives correct results if all the ids are in order. But if anyone of the id is deleted this logic fails.

Is there any other solution?

Why don't you just pass id instead of page (or both)? That would be easier and faster:SELECT id,imagePath,caption,count from images where id = $id — cwallenpoole
– cwallenpoole, Commented Jul 7, 2011 at 5:32
That would show the images in ascending order i want to show the recently added image first and so on. — Shashank amin
– Shashank amin, Commented Jul 7, 2011 at 6:38

Edgar Villegas Alvarado · Accepted Answer · 2011-07-07 05:07:12Z

1

You could do the following:

Adding another field, a 'sequential number' , so you have pairs ($id, $seq_number), and do your calculations as you did with $seq_number. Don't forget to update the sequential number field it on delete.
Get all the id's on an array, and calculate over there. In this option, the $id value is not used in the calculations, you use only the array indexes.

Hope this helps. Cheers

answered Jul 7, 2011 at 5:07

Edgar Villegas Alvarado

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1 Comment

Shashank amin Over a year ago

Thnaks will try it out and,soon let you know :)

nikc.org · Accepted Answer · 2011-07-07 05:21:56Z

1

I would suggest using something other than a running counter as the page-denominator. As you say, it is subject to change, or fail if a number is missing in between.

Your images have a caption. You could create a "slug" from that and use that as your page-denominator.

No more quirky maths or murky logic when creating links, no more disappearing pages.

answered Jul 7, 2011 at 5:21

nikc.org

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1 Comment

Shashank amin Over a year ago

Hey nice idea,Will surely use this in my future projects Thanks

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