方便以后制作php程序，直接拿来就可以用了，其实一些好的函数都在一些较成熟的cms系统中都有，例如dedecms，帝国cms,phpcms等，不论是gb2312的还是utf8格式的都有。

 
<? 
function GetIP() { //获取IP 
if ($_SERVER["HTTP_X_FORWARDED_FOR"]) 
$ip = $_SERVER["HTTP_X_FORWARDED_FOR"]; 
else if ($_SERVER["HTTP_CLIENT_IP"]) 
$ip = $_SERVER["HTTP_CLIENT_IP"]; 
else if ($_SERVER["REMOTE_ADDR"]) 
$ip = $_SERVER["REMOTE_ADDR"]; 
else if (getenv("HTTP_X_FORWARDED_FOR")) 
$ip = getenv("HTTP_X_FORWARDED_FOR"); 
else if (getenv("HTTP_CLIENT_IP")) 
$ip = getenv("HTTP_CLIENT_IP"); 
else if (getenv("REMOTE_ADDR")) 
$ip = getenv("REMOTE_ADDR"); 
else 
$ip = "Unknown"; 
return $ip; 
} 
?> 

 
<?php 
function DateAdd($date, $int, $unit = "d") { //时间的增加（还可以改进成时分秒都可以增加，有时间再补上） 
$dateArr = explode("-", $date); 
$value[$unit] = $int; 
return date("Y-m-d", mktime(0,0,0, $dateArr[1] + $value['m'], $dateArr[2] + $value['d'], $dateArr[0] + $value['y'])); 
} 
function GetWeekDay($date) { //计算出给出的日期是星期几 
$dateArr = explode("-", $date); 
return date("w", mktime(0,0,0,$dateArr[1],$dateArr[2],$dateArr[0])); 
} 
?> 

 
<? 
function check_date($date) { //检查日期是否合法日期 
$dateArr = explode("-", $date); 
if (is_numeric($dateArr[0]) && is_numeric($dateArr[1]) && is_numeric($dateArr[2])) { 
return checkdate($dateArr[1],$dateArr[2],$dateArr[0]); 
} 
return false; 
} 
function check_time($time) { //检查时间是否合法时间 
$timeArr = explode(":", $time); 
if (is_numeric($timeArr[0]) && is_numeric($timeArr[1]) && is_numeric($timeArr[2])) { 
if (($timeArr[0] >= 0 && $timeArr[0] <= 23) && ($timeArr[1] >= 0 && $timeArr[1] <= 59) && ($timeArr[2] >= 0 && $timeArr[2] <= 59)) 
return true; 
else 
return false; 
} 
return false; 
} 
function DateDiff($date1, $date2, $unit = "") { //时间比较函数，返回两个日期相差几秒、几分钟、几小时或几天 
switch ($unit) { 
case 's': 
$dividend = 1; 
break; 
case 'i': 
$dividend = 60; 
break; 
case 'h': 
$dividend = 3600; 
break; 
case 'd': 
$dividend = 86400; 
break; 
default: 
$dividend = 86400; 
} 
$time1 = strtotime($date1); 
$time2 = strtotime($date2); 
if ($time1 && $time2) 
return (float)($time1 - $time2) / $dividend; 
return false; 
} 
?> 

PHP重定向

 
<? 
方法一：header("Location: index.php"); 
方法二：echo "<scrīpt>window.location ="$PHP_SELF";</scrīpt>"; 
方法三：echo "<META HTTP-EQUIV="Refresh" CONTENT="0; URL=index.php">"; 
?> 

获取访问者浏览器

 
<? 
function browse_infor() 
{ 
$browser="";$browserver=""; 
$Browsers =array("Lynx","MOSAIC","AOL","Opera","JAVA","MacWeb","WebExplorer","OmniWeb"); 
$Agent = $GLOBALS["HTTP_USER_AGENT"]; 
for ($i=0; $i<=7; $i++) 
{ 
if (strpos($Agent,$Browsers[$i])) 
{ 
$browser = $Browsers[$i]; 
$browserver =""; 
} 
} 
if (ereg("Mozilla",$Agent) && !ereg("MSIE",$Agent)) 
{ 
$temp =explode("(", $Agent); $Part=$temp[0]; 
$temp =explode("/", $Part); $browserver=$temp[1]; 
$temp =explode(" ",$browserver); $browserver=$temp[0]; 
$browserver =preg_replace("/([d.]+)/","1",$browserver); 
$browserver = " $browserver"; 
$browser = "Netscape Navigator"; 
} 
if (ereg("Mozilla",$Agent) && ereg("Opera",$Agent)) 
{ 
$temp =explode("(", $Agent); $Part=$temp[1]; 
$temp =explode(")", $Part); $browserver=$temp[1]; 
$temp =explode(" ",$browserver);$browserver=$temp[2]; 
$browserver =preg_replace("/([d.]+)/","1",$browserver); 
$browserver = " $browserver"; 
$browser = "Opera"; 
} 
if (ereg("Mozilla",$Agent) && ereg("MSIE",$Agent)) 
{ 
$temp = explode("(", $Agent); $Part=$temp[1]; 
$temp = explode(";",$Part); $Part=$temp[1]; 
$temp = explode(" ",$Part);$browserver=$temp[2]; 
$browserver =preg_replace("/([d.]+)/","1",$browserver); 
$browserver = " $browserver"; 
$browser = "Internet Explorer"; 
} 
if ($browser!="") 
{ 
$browseinfo = "$browser$browserver"; 
} 
else 
{ 
$browseinfo = "Unknown"; 
} 
return $browseinfo; 
} 
//调用方法$browser=browseinfo() ;直接返回结果 
?> 

获取访问者操作系统

 
<? 
function osinfo() { 
$os=""; 
$Agent = $GLOBALS["HTTP_USER_AGENT"]; 
if (eregi('win',$Agent) && strpos($Agent, '95')) { 
$os="Windows 95"; 
} 
elseif (eregi('win 9x',$Agent) && strpos($Agent, '4.90')) { 
$os="Windows ME"; 
} 
elseif (eregi('win',$Agent) && ereg('98',$Agent)) { 
$os="Windows 98"; 
} 
elseif (eregi('win',$Agent) && eregi('nt 5.0',$Agent)) { 
$os="Windows 2000"; 
} 
elseif (eregi('win',$Agent) && eregi('nt',$Agent)) { 
$os="Windows NT"; 
} 
elseif (eregi('win',$Agent) && eregi('nt 5.1',$Agent)) { 
$os="Windows XP"; 
} 
elseif (eregi('win',$Agent) && ereg('32',$Agent)) { 
$os="Windows 32"; 
} 
elseif (eregi('linux',$Agent)) { 
$os="Linux"; 
} 
elseif (eregi('unix',$Agent)) { 
$os="Unix"; 
} 
elseif (eregi('sun',$Agent) && eregi('os',$Agent)) { 
$os="SunOS"; 
} 
elseif (eregi('ibm',$Agent) && eregi('os',$Agent)) { 
$os="IBM OS/2"; 
} 
elseif (eregi('Mac',$Agent) && eregi('PC',$Agent)) { 
$os="Macintosh"; 
} 
elseif (eregi('PowerPC',$Agent)) { 
$os="PowerPC"; 
} 
elseif (eregi('AIX',$Agent)) { 
$os="AIX"; 
} 
elseif (eregi('HPUX',$Agent)) { 
$os="HPUX"; 
} 
elseif (eregi('NetBSD',$Agent)) { 
$os="NetBSD"; 
} 
elseif (eregi('BSD',$Agent)) { 
$os="BSD"; 
} 
elseif (ereg('OSF1',$Agent)) { 
$os="OSF1"; 
} 
elseif (ereg('IRIX',$Agent)) { 
$os="IRIX"; 
} 
elseif (eregi('FreeBSD',$Agent)) { 
$os="FreeBSD"; 
} 
if ($os=='') $os = "Unknown"; 
return $os; 
} 
//调用方法$os=os_infor() ; 
?> 

文件格式类

 
<? 
$mime_types = array( 
'gif' => 'image/gif', 
'jpg' => 'image/jpeg', 
'jpeg' => 'image/jpeg', 
'jpe' => 'image/jpeg', 
'bmp' => 'image/bmp', 
'png' => 'image/png', 
'tif' => 'image/tiff', 
'tiff' => 'image/tiff', 
'pict' => 'image/x-pict', 
'pic' => 'image/x-pict', 
'pct' => 'image/x-pict', 
'tif' => 'image/tiff', 
'tiff' => 'image/tiff', 
'psd' => 'image/x-photoshop', 
'swf' => 'application/x-shockwave-flash', 
'js' => 'application/x-javascrīpt', 
'pdf' => 'application/pdf', 
'ps' => 'application/postscrīpt', 
'eps' => 'application/postscrīpt', 
'ai' => 'application/postscrīpt', 
'wmf' => 'application/x-msmetafile', 
'css' => 'text/css', 
'htm' => 'text/html', 
'html' => 'text/html', 
'txt' => 'text/plain', 
'xml' => 'text/xml', 
'wml' => 'text/wml', 
'wbmp' => 'image/vnd.wap.wbmp', 
'mid' => 'audio/midi', 
'wav' => 'audio/wav', 
'mp3' => 'audio/mpeg', 
'mp2' => 'audio/mpeg', 
'avi' => 'video/x-msvideo', 
'mpeg' => 'video/mpeg', 
'mpg' => 'video/mpeg', 
'qt' => 'video/quicktime', 
'mov' => 'video/quicktime', 
'lha' => 'application/x-lha', 
'lzh' => 'application/x-lha', 
'z' => 'application/x-compress', 
'gtar' => 'application/x-gtar', 
'gz' => 'application/x-gzip', 
'gzip' => 'application/x-gzip', 
'tgz' => 'application/x-gzip', 
'tar' => 'application/x-tar', 
'bz2' => 'application/bzip2', 
'zip' => 'application/zip', 
'arj' => 'application/x-arj', 
'rar' => 'application/x-rar-compressed', 
'hqx' => 'application/mac-binhex40', 
'sit' => 'application/x-stuffit', 
'bin' => 'application/x-macbinary', 
'uu' => 'text/x-uuencode', 
'uue' => 'text/x-uuencode', 
'latex'=> 'application/x-latex', 
'ltx' => 'application/x-latex', 
'tcl' => 'application/x-tcl', 
'pgp' => 'application/pgp', 
'asc' => 'application/pgp', 
'exe' => 'application/x-msdownload', 
'doc' => 'application/msword', 
'rtf' => 'application/rtf', 
'xls' => 'application/vnd.ms-excel', 
'ppt' => 'application/vnd.ms-powerpoint', 
'mdb' => 'application/x-msaccess', 
'wri' => 'application/x-mswrite', 
); 
?> 

php生成excel文档

 
<? 
header("Content-type:application/vnd.ms-excel"); 
header("Content-Disposition:filename=test.xls"); 
echo "test1t"; 
echo "test2tn"; 
echo "test1t"; 
echo "test2tn"; 
echo "test1t"; 
echo "test2tn"; 
echo "test1t"; 
echo "test2tn"; 
echo "test1t"; 
echo "test2tn"; 
echo "test1t"; 
echo "test2tn"; 
//改动相应文件头就可以输出.doc .xls等文件格式了 
?> 

时间比较问题
举一个简单例子说明:比如一个论坛对当天发表的贴子用new图片标记一下。
方法一：

 
<? 
//$db->rows[$i][date]中为数据库中datetime字段值. 
$today=time(); 
$theDay=date("Y-m-d H:i:s",$today-24*3600); 
$newTag=$db->rows[$i][date]>=$theDay?"<img src='../image/newinfor.gif'>":""; 
//方法二： 
$newTag=$db->rows[$i][date]>=date("Y-m-d 00:00:00")?"<img src='../image/newinfor.gif'>":""; 
?> 

 
//提取页面和浏览器提交的变量，作用相当于使PHP.INI开了全局变量 
<? 
@extract($_SERVER, EXTR_SKIP); 
@extract($_SESSION, EXTR_SKIP); 
@extract($_POST, EXTR_SKIP); 
@extract($_FILES, EXTR_SKIP); 
@extract($_GET, EXTR_SKIP); 
@extract($_ENV, EXTR_SKIP); 
?> 

//读取文件函数

 
<? 
function readfromfile($file_name) { 
if (file_exists($file_name)) { 
$filenum=fopen($file_name,"r"); 
flock($filenum,LOCK_EX); 
$file_data=fread($filenum, filesize($file_name)); 
rewind($filenum); 
fclose($filenum); 
return $file_data; 
} 
} 
?> 

//写入文件函数

 
<? 
function writetofile($file_name,$data,$method="w") { 
$filenum=fopen($file_name,$method); 
flock($filenum,LOCK_EX); 
$file_data=fwrite($filenum,$data); 
fclose($filenum); 
return $file_data; 
} 
?>