1、产生随机字符串函数

function random($length) {  
$hash = @#@#;  
$chars = @#ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz@#;  
$max = strlen($chars) - 1;  
mt_srand((double)microtime() * 1000000);  
for($i = 0; $i < $length; $i++) {  
  $hash .= $chars[mt_rand(0, $max)];  
}  
return $hash;  
} 

2、截取一定长度的字符串（该函数对GB2312使用有效）

function Wordscut($string, $length ,$sss=0) {  
if(strlen($string) > $length) {  
               if($sss){  
                      $length=$length - 3;  
                      $addstr=@# ...@#;  
                }  
  for($i = 0; $i < $length; $i++) {  
   if(ord($string[$i]) > 127) {  
    $wordscut .= $string[$i].$string[$i + 1];  
    $i++;  
   } else {  
    $wordscut .= $string[$i];  
   }  
  }  
  return $wordscut.$addstr;  
}  
return $string;  
} 

3、取得客户端IP地址

function GetIP(){  
             if (getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknown"))  
                   $ip = getenv("HTTP_CLIENT_IP");  
             else if (getenv("HTTP_X_FORWARDED_FOR") && strcasecmp(getenv("HTTP_X_FORWARDED_FOR"), "unknown"))  
                   $ip = getenv("HTTP_X_FORWARDED_FOR");  
             else if (getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR"), "unknown"))  
                   $ip = getenv("REMOTE_ADDR");  
             else if (isset($_SERVER[@#REMOTE_ADDR@#]) && $_SERVER[@#REMOTE_ADDR@#] && strcasecmp($_SERVER[@#REMOTE_ADDR@#], "unknown"))  
                   $ip = $_SERVER[@#REMOTE_ADDR@#];  
             else  
                  $ip = "unknown";  

             return($ip);  
} 

4、判断邮箱地址

function checkEmail($inAddress)  
{  
return (ereg("^([a-zA-Z0-9_-])+@([a-zA-Z0-9_-])+(\.[a-zA-Z0-9_-])+",$inAddress));  
} 

5、分页（两个函数配合使用）

function getpage($sql,$page_size=20)  
{  
      global $page,$totalpage,$sums;  //out param  
      $page = $_GET["page"];  
      //$eachpage = $page_size;  
      $pagesql = strstr($sql," from ");  
      $pagesql = "select count(*) as ids ".$pagesql;  
      $result = mysql_query($pagesql);  
      if($rs = mysql_fetch_array($result)) $sums = $rs[0];  
      $totalpage = ceil($sums/$page_size);  
      if((!$page)($page<1)) $page=1;  
   $startpos = ($page-1)*$page_size;  
   $sql .=" limit $startpos,$page_size ";  
    return $sql;  
}  
function showbar($string="")  
{       
    global $page,$totalpage;  
$out="共<font ".$totalpage."color=@#red@#><b>".$totalpage."</b></font>页  ";  
    $linkNum =4;  
    $start = ($page-round($linkNum/2))>0 ? ($page-round($linkNum/2)) : "1";  
    $end   = ($page+round($linkNum/2))<$totalpage ? ($page+round($linkNum/2)) : $totalpage;  
    $prestart=$start-1;  
    $nextend=$end+1;  
    if($page<>1)   
$out .= "<a href=@#?page=1&&".$string."@#title=第一页>第一页</a> ";  
    if($start>1)  
$out.="<a href=@#?page=".$prestart."@# title=上一页>..<<</a> ";  

for($t=$start;$t<=$end;$t++)  
    {  
     $out .= ($page==$t) ? "<font [".$t."]color=@#red@#><b>[".$t."]</b></font> " : "<a $thref=@#?page=$t&&".$string."@#>$t</a> ";  
    }  
if($end<$totalpage)  
$out.="<a href=@#?page=".$nextend."&&".$string."@# title=下一页>>>..</a>";  
    if($page<>$totalpage)  
   $out .= " <a href=@#?page=".$totalpage."&&".$string."@# title=最后页>最后页</a>";  
   return $out;  
} 

6、获取新插入数据的ID

<?  
mysql_insert_id();  
?>