Php paging principle

Php paging principle 1. first understand the limit usage in SQL statements

SELECT * FROM table ...... Limit start position, number of operations (where the start position starts from 0)

Example:

Take the first 20 records: SELECT * FROM table ...... Limit 0, 20
Obtain 20 records FROM 11th: SELECT * FROM table ...... Limit 10, 20

LIMIT n is equivalent to LIMIT 0, n.

For example, select * from table LIMIT 5; // return the first five rows, the same as select * from table LIMIT

2. paging principle

The so-called paging display, that is, the result set in the database, is displayed in a segment

How to segment, the current segment (the number of lines per page, and the number of pages next)

First 10 records: select * from table limit 0, 10
11th to 20 records: select * from table limit 10, 10
21st to 30 records: select * from table limit 20, 10

Paging formula:

(Current page-1) X number of entries per page, number of entries per page
Select * from table limit ($ Page-1) * $ PageSize, $ PageSize

3. $ _ SERVER ["REQUEST_URI"] function

A type of predefined SERVER variables. all variables starting with $ _ SERVER are called SERVER variables.

REQUEST_URI is used to obtain the current URI, which is the complete address path after the domain name.

Example:

The current page is: http://www.test.com/home.php? Id = 23 & cid = 22

Echo $ _ SERVER ["REQUEST_URI"]

Result:/home. php? Id = 23 & cid = 22

4. parse_url () parses the URL function.

Parse_url () is a function that parses a URL into an array with a fixed key value.

Example
$ Ua = parse_url ("http: // username: password @ hostname/path? Arg = value # anchor ");
Print_r ($ ua );
Result:

Array
(
[Scheme] => http; protocol
[Host] => hostname; host domain name

[User] => username; user
[Pass] => password; password
[Path] =>/path; path
[Query] => arg = value; obtain the parameter

[Fragment] => anchor;
)

5. code example

The page for this message is divided into three parts: database design, connection page, and display page.

(1) design a database

The database name is bbs. there is a data table named message, which contains the title, lastdate, user, content and other fields, indicating the message title, message date, message recipient, and message content.

(2) connection page

$ Conn = @ mysql_connect ("localhost", "root", "123456") or die ("database link error ");
Mysql_select_db ("bbs", $ conn );
Mysql_query ("set names 'gbk'"); // use GBK Chinese encoding;

// Convert spaces and line breaks into HTML parses

Function htmtocode ($ content ){
$ Content = str_replace ("\ n ","
", Str_replace (" "," ", $ content); // Two str_replace nesting

Return $ content;
}

// $ Content = str_replace ("'", "'", $ content );
// Htmlspecialchars ();

(3) display page

Include ("conn. php ");

$ Pagesize = 2; // set to display 2 records per page
$ Url = $ _ SERVER ["REQUEST_URI"];
$ Url = parse_url ($ url );
$ Url = $ url [path];

$ Numq = mysql_query ("SELECT * FROM 'message "');
$ Num = mysql_num_rows ($ numq );

If ($ _ GET [page]) {
$ Pageval = $ _ GET [page];
$ Page = ($ pageval-1) * $ pagesize;
$ Page. = ',';
}
If ($ num> $ pagesize ){
If ($ pageval <= 1) $ pageval = 1;

Echo "$ num total ".
"Next page of the previous page ";
}
$ SQL = "SELECT * FROM 'message' limit $ page $ pagesize ";
$ Query = mysql_query ($ SQL );

While ($ row = mysql_fetch_array ($ query )){
?>

Title:	Time:
User:
Content:

}
?>
(4) Last display