Question

I have been trying to resolve a paging problem and I do not understand the following code.

                $lstart = ($page * 6) -6;
                $lend = ($page * 6)-1;
                $limit = $lstart.','.$lend;

The results I get are mixed. I should get six articles per page, but it is inconsistent. The code is incorporated in a script I inherited from someone else and I am trying to fix it. Can someone explain this code to me? In the query, LIMIT=$limit.

Answer 1

It should be…

$lstart = ($page * 6) -6; // quite frankly, it's clearer to write...
       // ($page - 1) * 6
$limit = $lstart.',6';

The second clause in limit declares how many items. Not up to a certain point.

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From mysql docs: (copy/paste)

SELECT * FROM tbl LIMIT 5,10;  # Retrieve rows 6-15

So, 1,10 would be rows 2-11
Thus, to get row 1, you need to set the offset to zero: 0,10 which would give you rows 1-10.

You can also check out further tutorials on LIMIT here: http://php.about.com/od/mysqlcommands/g/Limit_sql.htm

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Code with explanation.

$rows_per_page = 6; // you're trying to get 6 rows for every "page".

// On page 1, you'd want rows 0-5 (6 rows inclusively)
// On page 2, you'd want rows 6-111 (again, 6 rows inclusively)
// and so forth.
// So when $page == 1, you want to start at 0, on page 2, start at 6....
// To express this pattern mathematically, we write:
$start = ($page - 1) * 6

// mysql takes offset and number as it's two variables in the LIMIT clause, 
// in that order, when two are provided.
// So we write:
$query = "SELECT * FROM table WHERE 1 LIMIT $start, $rows_per_page;";

// So, at page 1, you get
$query = "SELECT * FROM table WHERE 1 LIMIT 0, 6;"; // if we were to substitute the variables.
$query = "SELECT * FROM table WHERE 1 LIMIT 6, 6;"; // at page 2
$query = "SELECT * FROM table WHERE 1 LIMIT 12, 6;"; // at page 3