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PHP paging principle and page jump examples

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WBOYOriginal
2016-07-25 08:52:461621browse
  1. select * from table limit 0,10 // The first 10 records
  2. select * from table limit 10,10 // The 11th to 20th records
  3. select * from table limit 20,10 // The 21st to 20th records 30 records
  4. ...
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This set of sql statements is actually the sql statement for fetching each page of data in the table when $pagesize=10. We can summarize such a template: select * from table limit ($currentpageid - 1) * $pagesize, $pagesize Take this template and substitute the corresponding values ​​​​and compare it with the above set of sql statements to see if that is the case. After solving the most important problem of how to obtain the data, all that is left is to pass the parameters, construct the appropriate SQL statement and then use PHP to obtain the data from the database and display it.

php paging code:

  1. // Establish database connection
  2. $link = mysql_connect("localhost", "mysql_user", "mysql_password")
  3. or die("could not connect: " . mysql_error());
  4. // Get the current page number
  5. if( isset($_get['page']) ){
  6. $page = intval( $_get['page'] );
  7. }
  8. else{
  9. $page = 1;
  10. }
  11. // Number of pages per page
  12. $pagesize = 10;
  13. // Get the total amount of data
  14. $sql = "select count(*) as amount from table";
  15. $result = mysql_query($sql);
  16. $row = mysql_fetch_row ($result);
  17. $amount = $row['amount'];
  18. // Calculate how many pages there are in total
  19. if( $amount ){
  20. if( $amount < $page_size ){ $page_count = 1; } //If the total data amount is less than $pagesize, then there is only one page
  21. if( $amount % $page_size ){ //The remainder of dividing the total data amount by the number of pages
  22. $page_count = (int)($amount / $page_size ) + 1; //If there is a remainder, the number of pages is equal to the total data amount divided by the number of pages, rounded up and plus one
  23. }else{
  24. $page_count = $amount / $page_size; //If there is no remainder, then The number of pages is equal to the total amount of data divided by the number of pages per page
  25. }
  26. }
  27. else{
  28. $page_count = 0;
  29. }
  30. // Page turning link
  31. $page_string = '';
  32. if( $page == 1 ){
  33. $page_string .= 'First page|Previous page|';
  34. }
  35. else{
  36. $page_string .= 'Previous page|';
  37. }
  38. if( ($page == $page_count) | | ($page_count == 0) ){
  39. $page_string .= 'next page|last page';
  40. }
  41. else{
  42. $page_string .= 'Next page|Last page';
  43. }
  44. // Get data and return the result in two-dimensional array format
  45. if( $amount ){
  46. $sql = "select * from table order by id desc limit ". ($page-1)*$page_size .", $page_size";
  47. $result = mysql_query($sql);
  48. while ( $row = mysql_fetch_row($result) ){
  49. $rowset[] = $row;
  50. }
  51. }else{
  52. $rowset = array();
  53. }
  54. / / There is no code to display the results, so that is beyond the scope of the discussion. You can simply use the obtained two-dimensional array to display the results using foreach
  55. ?>
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oo style code, the database connection in the following code is processed using the pear db class

  1. // filename: pager.class.php
  2. // Paging class, this class is only used to process data structures and is not responsible for processing display work
  3. class pager
  4. {
  5. var $pagesize ; //Number of each page
  6. var $currentpageid; //Current page number
  7. var $nextpageid; //Next page
  8. var $previouspageid; //Previous page
  9. var $numpages; //Total number of pages
  10. var $numitems; //Total number of records
  11. var $isfirstpage; //Whether it is the first page
  12. var $islastpage; //Whether it is the last page
  13. var $sql; //SQL query statement
  14. function pager($option)
  15. {
  16. global $db;
  17. $this->_setoptions($option);
  18. // Total number of items
  19. if ( !isset($this->numitems) )
  20. {
  21. $res = $db->query( $this->sql);
  22. $this->numitems = $res->numrows();
  23. }
  24. // Total number of pages
  25. if ( $this->numitems > 0 )
  26. {
  27. if ( $this->numitems < $this->pagesize ){ $this->numpages = 1; }
  28. if ( $this->numitems % $this->pagesize )
  29. {
  30. $this- >numpages= (int)($this->numitems / $this->pagesize) + 1;
  31. }
  32. else
  33. {
  34. $this->numpages = $this->numitems / $this-> ;pagesize;
  35. }
  36. }
  37. else
  38. {
  39. $this->numpages = 0;
  40. }
  41. switch ( $this->currentpageid )
  42. {
  43. case $this->numpages == 1:
  44. $ this->isfirstpage = true;
  45. $this->islastpage = true;
  46. break;
  47. case 1:
  48. $this->isfirstpage = true;
  49. $this->islastpage = false;
  50. break;
  51. case $this->numpages:
  52. $this->isfirstpage = false;
  53. $this->islastpage = true;
  54. break;
  55. default:
  56. $this->isfirstpage = false;
  57. $this->islastpage = false;
  58. }
  59. if ( $this->numpages > 1 )
  60. {
  61. if ( !$this->islastpage ) { $this->nextpageid = $this->currentpageid + 1; }
  62. if ( !$this->isfirstpage ) { $this->previouspageid = $this->currentpageid - 1; }
  63. }
  64. return true;
  65. }
  66. /***
  67. *
  68. * Returns the database connection of the result set
  69. * When the result set is relatively large, you can directly use this method to obtain the database connection, and then traverse outside the class, which has less overhead
  70. * If the result set is not very large, you can Directly use getpagedata to obtain the result in two-dimensional array format
  71. * The getpagedata method also calls this method to obtain the result
  72. *
  73. ***/
  74. function getdatalink()
  75. {
  76. if ( $this->numitems )
  77. {
  78. global $db;
  79. $pageid = $this->currentpageid;
  80. $from = ($pageid - 1)*$this- >pagesize;
  81. $count = $this->pagesize;
  82. $link = $db->limitquery($this->sql, $from, $count); //Use pear db::limitquery method to ensure Database compatibility
  83. return $link;
  84. }
  85. else
  86. {
  87. return false;
  88. }
  89. }
  90. /***
  91. *
  92. * Return the result set in the format of a two-dimensional array
  93. *
  94. ***/
  95. function getpagedata()
  96. {
  97. if ( $this->numitems )
  98. {
  99. if ( $res = $this->getdatalink() )
  100. {
  101. if ( $res->numrows() )
  102. {
  103. while ( $row = $res->fetchrow() )
  104. {
  105. $result[] = $row;
  106. }
  107. }
  108. else
  109. {
  110. $result = array();
  111. }
  112. return $result;
  113. }
  114. else
  115. {
  116. return false;
  117. }
  118. }
  119. else
  120. {
  121. return false;
  122. }
  123. }
  124. function _setoptions($option)
  125. {
  126. $allow_options = array(
  127. 'pagesize',
  128. 'currentpageid',
  129. 'sql',
  130. 'numitems'
  131. );
  132. foreach ( $option as $key => $value )
  133. {
  134. if ( in_array($key, $allow_options) && ($value != null) )
  135. {
  136. $this->$key = $value;
  137. }
  138. }
  139. return true;
  140. }
  141. }
  142. ?>
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Pagination code call:

  1. // filename: test_pager.php
  2. // This is a simple sample code, the code for using the pear db class to establish a database connection is omitted
  3. require "pager.class.php" ;
  4. if ( isset($_get['page']) )
  5. {
  6. $page = (int)$_get['page'];
  7. }
  8. else
  9. {
  10. $page = 1;
  11. }
  12. $sql = "select * from table order by id";
  13. $pager_option = array(
  14. "sql" => $sql,
  15. "pagesize" => 10,
  16. "currentpageid" => $page
  17. );
  18. if ( isset($_get['numitems']) )
  19. {
  20. $pager_option['numitems'] = (int)$_get['numitems'];
  21. }
  22. $pager = @new pager($pager_option);
  23. $data = $pager->getpagedata();
  24. if ( $pager->isfirstpage )
  25. {
  26. $turnover = "Homepage|Previous page|";
  27. }
  28. else
  29. {
  30. $turnover = "Homepage|previouspageid."&numitems=" .$pager->numitems."'>Previous page|";
  31. }
  32. if ( $pager->islastpage )
  33. {
  34. $turnover .= "Next page | Last page" ;
  35. }
  36. else
  37. {
  38. $turnover .= "nextpageid."&numitems=".$pager->numitems."'>next Page|numpages."&numitems=".$pager->numitems."'>Last Page" ;
  39. }
  40. ?>
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Instructions: This class only processes data and is not responsible for display, because it is a bit reluctant to put both data processing and result display into one class. The situation and requirements during display are changeable. It is better to process it according to the results given by the class. A better way is to inherit a subclass of your own based on the pager class to display different paginations. For example, to display the user pagination list:

  1. class memberpager extends pager
  2. {
  3. function showmemberlist()
  4. {
  5. global $db;
  6. $data = $this->getpagedata();
  7. // Code to display the results
  8. // ......
  9. }
  10. }
  11. /// Call
  12. if ( isset($_get['page']) )
  13. {
  14. $page = (int)$_get['page'];
  15. }
  16. else
  17. {
  18. $page = 1;
  19. }
  20. $sql = "select * from members order by id";
  21. $pager_option = array(
  22. "sql" => $sql,
  23. "pagesize" => 10,
  24. "currentpageid" => $page
  25. );
  26. if ( isset($_get['numitems']) )
  27. {
  28. $pager_option['numitems'] = (int)$_get['numitems'];
  29. }
  30. $pager = @new memberpager($pager_option);
  31. $pager->showmemberlist();
  32. ?>
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Second, the compatibility of different databases in different databases The way to write a section of intercepted results is different.

  1. $pagenum=@ceil($num/$pagesize);
  2. if($num > $pagesize){
  3. if($ pageval<=1) $pageval=1;
  4. if($pageval==$pagenum){
  5. echo "Homepage Previous page Next page < a href='$url?page=".$pagenum."'>Last page";
  6. //echo "page".$pageval."/total".$pagenum."page" ;
  7. echo " to pages of $pagenum pages";
  8. }
  9. }
  10. }
  11. ?>
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