function Pager($option)
{
global $db;
$this->_setOptions($option);
// 总条数
if ( !isset($this->numItems) )
{
$res = $db->query($this->sql);
$this->numItems = $res->numRows();
}
// 总页数
if ( $this->numItems > 0 )
{
if ( $this->numItems < $this->PageSize ){ $this->numPages = 1; }
if ( $this->numItems % $this->PageSize )
{
$this->numPages= (int)($this->numItems / $this->PageSize) + 1;
}
else
{
$this->numPages = $this->numItems / $this->PageSize;
}
}
else
{
$this->numPages = 0;
}

switch ( $this->CurrentPageID )
{
case $this->numPages == 1:
$this->isFirstPage = true;
$this->isLastPage = true;
break;
case 1:
$this->isFirstPage = true;
$this->isLastPage = false;
break;
case $this->numPages:
$this->isFirstPage = false;
$this->isLastPage = true;
break;
default:
$this->isFirstPage = false;
$this->isLastPage = false;
}

if ( $this->numPages > 1 )
{
if ( !$this->isLastPage ) { $this->NextPageID = $this->CurrentPageID + 1; }
if ( !$this->isFirstPage ) { $this->PrevIoUsPageID = $this->CurrentPageID - 1; }
}

return true;
}

/***

• 返回结果集的数据库连接
• 在结果集比较大的时候可以直接使用这个方法获得数据库连接，然后在类之外遍历，这样开销较小
• 如果结果集不是很大，可以直接使用getPageData的方式获取二维数组格式的结果
• getPageData方法也是调用本方法来获取结果的

• ***/

function getDataLink()
{
if ( $this->numItems )
{
global $db;

$PageID = $this->CurrentPageID;

$from = ($PageID - 1)*$this->PageSize;
$count = $this->PageSize;
$link = $db->limitQuery($this->sql,$from,$count); //使用Pear DB::limitQuery方法保证数据库兼容性

return $link;
}
else
{
return false;
}
}

/***

• 以二维数组的格式返回结果集

• ***/

function getPageData()
{
if ( $this->numItems )
{
if ( $res = $this->getDataLink() )
{
if ( $res->numRows() )
{
while ( $row = $res->fetchRow() )
{
$result[] = $row;
}
}
else
{
$result = array();
}

return $result;
}
else
{
return false;
}
}
else
{
return false;
}
}

function _setOptions($option)
{
$allow_options = array(
'PageSize',
'CurrentPageID',
'sql',
'numItems'
);

foreach ( $option as $key => $value )
{
if ( in_array($key,$allow_options) && ($value != null) )
{
$this->$key = $value;
}
}

return true;
}
}
?>