PHP Paging principle + page code + pagination class production

Pagination display is a very common way to browse and display large amounts of data, which is one of the most frequently handled events in Web programming. For the veteran of Web programming, writing this code is just as natural as breathing, but for beginners, there is often no clue to the problem, so write this article specifically to explain the problem in detail.

first, the principle of paging:
The so-called paging display, that is, the result set in the database is artificially divided into a section of the display, here requires two initial parameters:

How many records per page ($PageSize)?
What is the current page ($CurrentPageID)?

Now just give me a result set and I can show a specific result.

For other parameters, such as the previous page ($PReviousPageID), the next page ($NextPageID), the total number of pages ($numPages), and so on, can be based on the front of these things.

For example, in MySQL database, if you want to intercept a piece of content from within a table, the SQL statement can be used: SELECT * FROM table limit offset, rows. Take a look at the following set of SQL statements and try to find out the rate of compliance.

Top 10 Records: SELECT * FROM table limit 0,10
11th to 20th record: SELECT * FROM table limit 10,10
21st to 30th Record: SELECT * FROM table limit 20,10
......
This set of SQL statements is actually a SQL statement that takes every page of data in the table when $pagesize=10, and we can summarize a template like this:
SELECT * FROM table limit ($CurrentPageID-1) * $PageSize, $PageSize
Take this template and replace the corresponding value with the set of SQL statements above to see if that's the case. Take care of the most important question of how to get the data, all that is left is to pass the parameters, construct the appropriate SQL statement, and then use PHP to retrieve the data from the database and display it.


Two, paging code Description: Five Steps

The code is fully explained and can be copied to your own Notepad directly using

8. <meta http-equiv= "Content-type" content= "Text/html;charset=utf-8"/>
10. <title> Employee Information List </title>
14. <?php
16. Display information for all EMP tables
18. 1. Connect to the database
20. $conn =mysql_connect (' localhost ', ' root ', ' 1234abcd ') or Die (' Connection Database error '. mysql_error ());
22. 2. Select a database
24. mysql_select_db (' empmanage ');
26. 3. Select a character Set
28. mysql_query (' Set names UTF8 ');
30. 4. Send SQL statements and get results for processing
32. 4.1 Paging [paging to emit two SQL statements, one to get $rowcount, and one to get paged results through the limit of SQL. So we're going to get two result sets and remember to distinguish them when naming them.
34. Paging (four values of two SQL statements). ]
36. $pageSize =3;//How many records are displayed per page
38. How many records are there in $rowCount =0;//?
40. $pageNow =1;//want to display the first few pages
42. $pageCount =0;//altogether have how many pages [pagination altogether this four indicators, is indispensable. Since $rowcount can be obtained from the server, it can be given an initial value of 0;
44. $pageNow want to display the first few pages, it is best to set to 0, $pageSize is the number of records per page, which is based on the requirements of the site in advance.
46. $pageCount =ceil ($rowCount/$pageSize), since $rowcount can have an initial value of 0, the $pagecount can of course be set to 0. Four indicators, two 0, one 1, and the other for website requirements. ]
48. 4.15 Modify the value of the $pagenow according to the paging link
50. if (!empty ($_get[' Pagenow ')) {
52. $pageNow =$_get[' Pagenow '];
54. }[modifies the value of $pagenow according to the paging link. ]
56. $sql = ' SELECT count (ID) from EMP ';
58. $res 1=mysql_query ($sql);
60. 4.11 Number of rows removed
62. if ($row =mysql_fetch_row ($res 1)) {
64. $rowCount = $row [0];
66. }//[get $rowcount,, into the We will know $pagecount these two indicators. ]
68. 4.12 Calculate the total number of pages
70. $pageCount =ceil ($rowCount/$pageSize);
72. $pageStart = ($pageNow-1) * $pageSize;
76. 4.13 Sending SQL results with paging
78. $sql = "SELECT * from emp limit $pageStart, $pageSize";//[paging is implemented based on the two values (starting value, per page number) following the limit of the $sql statement. And the two values are evaluated. ]
80. $res 2=mysql_query ($sql, $conn) or die (' cannot get result set '. Mysql_error ());
82. Echo ' <table border=1> '; [echo "<table border= ' 1px ' cellspacing= ' 0px ' bordercolor= ' red ' width= ' 600px ' >";]
84. "<tr><th>id</th><th>name</th><th>grade</th><th>email</th ><th>salary</th><th><a href= ' # ' > Delete user </a></th><th><a href= ' # ' >        Modify User </a></th></tr> "; while ($row =mysql_fetch_assoc ($res 2)) {
86. echo "<tr><td>{$row [' id ']}</td><td>{$row [' name ']}</td><td>{$row [' Grade ']} </td><td>{$row [' email ']}</td><td>{$row [' Salary ']}</td><td><a href= ' # '        > Delete User </a></td><td><a href= ' # ' > Modify User </a></td></tr> "; }
88. Echo ' </table> ';
90. 4.14 Print out a hyperlink to a page number
92. for ($i =1; $i <= $pageCount; $i + +) {
94. echo "<a href= '? pagenow= $i ' > $i </a>"//[print out the page number of hyperlinks]
98. }
100. 5. Release the resource, close the connection
102. Mysql_free_result ($res 2);
104. Mysql_close ($conn);
106. ?>

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Third, simple paging class sharing

Now publish a simple sorting production. As long as you understand the principles and procedures of this class, other complex classes can be comprehend by analogy. No nonsense, directly on the source, you can directly use in your project.

Database Operation Class Code: mysqli.func.php

2. <?php
4. Database Connection Constants
6. Define (' db_host ', ' localhost ');
8. Define (' Db_user ', ' root ');
10. Define (' db_pwd ', ');
12. Define (' Db_name ', ' guest ');
16. Connecting to a database
18. Function Conn ()
20. {
22. $conn = Mysqli_connect (Db_host, Db_user, Db_pwd, db_name);
24. Mysqli_query ($conn, "Set names UTF8");
26. return $conn;
28. }
32. Get the result set
34. function Doresult ($sql) {
36. $result =mysqli_query (Conn (), $sql);
38. return $result;
40. }
44. Result set to object collection
46. function Dolists ($result) {
48. Return Mysqli_fetch_array ($result, MYSQL_ASSOC);
50. }
54. function Totalnums ($sql) {
56. $result =mysqli_query (Conn (), $sql);
58. return $result->num_rows;
60. }
66. Close the database
68. function Closedb ()
70. {
72. if (! Mysqli_close ()) {
74. Exit (' close exception ');
76. }
78. }
82. ?>

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Pagination Implementation code:

What's hidden in this post

2. <?php
4. Include ' mysqli.func.php ';
8. Total Record Count
10. $sql = "Select dg_id from Tb_user";
12. $totalnums = Totalnums ($sql);
16. Show number of bars per page
18. $fnum = 8;
22. Number of pages
24. $pagenum = Ceil ($totalnums/$fnum);
28. Page Constants
30. @ $tmp = $_get[' page '];
34. Prevent malicious paging
36. if ($tmp > $pagenum)
38. echo "<script>window.location.href= ' index.php ' </script>";
42. Calculate Paging Start value
44. if ($tmp = = "") {
46. $num = 0;
48. } else {
50. $num = ($tmp-1) * $FNUM;
52. }
56. Query statements
58. $sql = "Select Dg_id,dg_username from Tb_user ORDER by dg_id DESC LIMIT". $num. ", $fnum";
60. $result = Doresult ($sql);
64. Traverse output
66. while (!! $rows = dolists ($result)) {
68. echo $rows [' dg_id ']. " " . $rows [' Dg_username ']. "<br>";
70. }
74. Page link
76. for ($i = 0; $i < $pagenum; $i + +) {
78. echo "<a href=index.php?page=". ($i + 1). ">". ($i + 1). "</a>";
80. }
84. ?>

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PHP Paging principle + page code + pagination class production