php pagination

<?php
/**
 *
 * Get paginated HTML content
 * @param integer $page current page
 * @param integer $pages total number of pages
 * @param string $url The last page number of the jump url address is appended to the url with '&page=x'
 *
 *
 * @return string HTML content;
 */
 function getPageHtml($page, $pages, $url){
    // How many page numbers to display at most
    $_pageNum = 5;
    //If the current page is less than 1, it is 1
    $page = $page<1?1:$page;
    //The current page is greater than the total number of pages, the total number of pages
    $page = $page > $pages ? $pages : $page;
    //The current page is the current page if the number of pages is small
    $pages = $pages < $page ? $page : $pages;

    //calculate start page
    $_start = $page - floor($_pageNum/2);
    $_start = $_start<1 ? 1 : $_start;
    //calculate the end page
    $_end = $page + floor($_pageNum/2);
    $_end = $_end>$pages? $pages : $_end;

    //The number of currently displayed page numbers is not enough for the maximum number of pages, and is being adjusted left and right
    $_curPageNum = $_end-$_start+1;
    // left adjustment
    if($_curPageNum<$_pageNum && $_start>1){
        $_start = $_start - ($_pageNum-$_curPageNum);
        $_start = $_start<1 ? 1 : $_start;
        $_curPageNum = $_end-$_start+1;
    }
    // right adjustment
    if($_curPageNum<$_pageNum && $_end<$pages){
        $_end = $_end + ($_pageNum-$_curPageNum);
        $_end = $_end>$pages? $pages : $_end;
    }

    $_pageHtml = '<ul class="pagination">';
    /*if($_start == 1){
     $_pageHtml .= '<li><a title="第一页">«</a></li>';
     }else{
     $_pageHtml .= '<li><a  title="第一页" href="'.$url.'&page=1">«</a></li>';
     }*/
    if($page>1){
        $_pageHtml .= '<li><a  title="上一页" href="'.$url.'&page='.($page-1).'">«</a></li>';
    }
    for ($i = $_start; $i <= $_end; $i++) {
        if($i == $page){
            $_pageHtml .= '<li class="active"><a>'.$i.'</a></li>';
        }else{
            $_pageHtml .= '<li><a href="'.$url.'&page='.$i.'">'.$i.'</a></li>';
        }
    }
    /*if($_end == $pages){
     $_pageHtml .= '<li><a title="Last page">»</a></li>';
     }else{
     $_pageHtml .= '<li><a  title="最后一页" href="'.$url.'&page='.$pages.'">»</a></li>';
     }*/
    if($page<$_end){
        $_pageHtml .= '<li><a  title="下一页" href="'.$url.'&page='.($page+1).'">»</a></li>';
    }
    $_pageHtml .= '</ul>';
    echo $_pageHtml;
}

getPageHtml($_GET['page'], 50, '/page.php?');