PHP simple paging principle and paging code examples

/*******Page Principle*************/
//Display the number of records per page
$page_size = 3;
$sql = "select * from message";
 $result = mysql_query($sql);
//Total number of records
$num = mysql_num_rows($result);
//Calculation of total number of pages
if($num<= $page_size) { $page_count =1; }
if($num%$page_size) { $page_count = intval($num/$page_size)+1;}
if($num%$page_size==0) { $page_count = $num/$page_size ;}

if( isset($_GET['page']) ){
 $page = intval($_GET['page']);
}
else{
 $page = 1;
}

$sql_page= "select * from message limit ".($page-1)*$page_size.",$page_size";
$do = mysql_query($sql_page);
while( $re = mysql_fetch_object($ do)){
 echo 'Write anything you want';
}

if($page<>1){
 echo 'Homepage';
 echo 'Previous page';
}

if($page<>$page_count){
 echo '';
 echo 'Next page';
 echo 'Last Night';
 echo '< /div>';
}