Question

I’m sorry, I am a newbie in PHP. Now I want to learn how to write a pagination effect in PHP. I know there are many tutorials for this on the net. I searched it and have a reference to them. When I try it by myself and don’t have a reference to other resources, though, I still don’t know how to write a pagination effect with PHP.

Now, I want to know what’s the basic and important thing of writing a pagination in PHP. If anyone could give me more details, thank you.

Answer 1

For this example, I will use MySQL because it’s a popular database to use with PHP. The general principle applies to other databases, but the precise way you use SQL to achieve the results is different.

The essence of pagination is that you have a number records, say 105, and you only want to display a smaller, more manageable number of records at a time, say 10 of them. In order to do this, you need to know how to find out the total number of records, and you need to know how to select just a subset of the records.

First, find out how many records you have. For this, you use COUNT(*) to count the records in the table. If your table is called Users:

SELECT COUNT(*) FROM Users;

Since we said there are 105 records in the table, this will return the result 105. We said each page has 10 records, so figure out how many pages there are in total: 105 / 10 = 10.5; round up to 11 because the extra records after page 10 need their own page. So, there are 11 pages in total. Your web page will display controls that enable the user to select a page from 1 to 11.

Instead of fetching all the records, you will only fetch one page at a time. In MySQL you generally do this using the LIMIT keyword; this allows you to choose a range of records. LIMIT syntax works like this: LIMIT $SKIP, $COUNT, where $SKIP is the number of records in the result set to skip, and $COUNT is the number to return. (Actually, you will get up to $COUNT records, in case fewer are available.)

The user has requested page 6. This means that I need to skip 5 pages before the results I want to show. With pages of 10 records each, this means I will skip 5 * 10 records, i.e. 50 records. In other words, $SKIP = ($PAGE_NUMBER - 1) * $PAGE_SIZE. You query would look like this:

SELECT User_ID, UserName, City, State from Users LIMIT 50, 10;

This gives you records 51-60 of the table.

See the documentation to learn more about how LIMIT works:

http://dev.mysql.com/doc/refman/5.5/en/select.html

Now you have a single page of records. However, the numbering of the records is dependent on their ordering. The query above will give you unpredictable results because the ordering is undefined. (A database can return records in any order it chooses unless you command it to use a certain ordering.) Thus, to do pagination, you need to define the order of the records. Use ORDER BY to define the ordering:

SELECT User_ID, UserName, City, State from Users ORDER BY UserName LIMIT 50, 10;

This allows you to show different pages of results, and always know that when you show page 6, it contains the records that come after the ones on page 5 and before the ones on page 7.

(If your records don’t have any natural ordering, you will have to define an arbitrary one to make this work correctly.)

I have avoided mentioning PHP at all in this answer because I don’t think it’s necessary to do so to explain pagination. Pagination is entirely a matter of handling data. If you understand this, I think you can go read the tutorials and they will make sense to you and then you can figure how to write the PHP to do this.